Method for producing an article for use in the foundry industry, corresponding granular material and kit, apparatuses, and uses

ABSTRACT

The invention relates to a method for producing an article for use in the foundry industry, selected from a group consisting of granular material for producing a pourable additive, a solid pourable additive, an inorganic binder, and a molding material mixture. The invention also relates to a corresponding granular material comprising particulate amorphous silica and to a kit for producing an inorganic binder. The invention also relates to an apparatus for carrying out the method according to the invention and to a corresponding use of particulate amorphous silica and to the corresponding use of a granular material.

The present invention relates to a process for producing an article foruse in the foundry industry, selected from the group consisting ofgranular material for production of a pourable additive, solid pourableadditive, inorganic binder and molding material mixture. Further detailsof the process of the invention will be apparent from the appendedclaims and from the description that follows. The present inventionadditionally relates to a corresponding granular material comprisingparticulate amorphous silicon dioxide. The present invention furtherrelates to a kit for production of an inorganic binder. The presentinvention also relates to an apparatus for performance of the process ofthe invention. The present invention further relates to a correspondinguse of particulate amorphous silicon dioxide. The present inventionadditionally relates to the corresponding use of a granular material.Details of each will be apparent from the appended claims and thedescription that follows.

Casting in a lost mold is a widely used process for producingnear-net-shape components. After the casting, the mold is destroyed, andthe cast part is removed. Lost molds are casting molds and hencenegatives; they contain the cavity to be cast that results in thefinished cast part. The inner contours of the future cast part areformed by cores. In the production of the casting mold, a model of thecast part to be manufactured forms the cavity in the molding material.

By contrast with sand casting methods in which the casting molds (lostmolds) are destroyed after casting to remove the cast part, metallicpermanent molds, manufactured from cast iron or steel for example, canbe reutilized for the next casting after the cast part has been removed.It is also possible to work by diecasting, in which case the liquidmetal melt is injected into a diecasting mold under high pressure at ahigh mold filling rate. The aforementioned casting methods are alsopreferred in the context of the present invention. Mold base materialsused for casting molds (in sand casting methods with lost molds) andcores are predominantly refractory grainy substances, for example washedclassified quartz sand. For production of the casting molds, the moldbase materials are bound with inorganic or organic binders. The bindercreates fixed coherence between the particles of the mold base material,such that the casting mold or core gains the requisite mechanicalstability. The refractory mold base material premixed with the binder ispreferably in a free-flowing form, such that it can be introduced into asuitable cavity and compacted therein. The molding materials arecompacted in order to increase strength.

Casting molds and cores must fulfill various demands. During the actualcasting operation, they must first have sufficient strength and thermalstability to be able to accommodate the liquid metal in the cavityformed from one or more (partial) casting molds. After the solidifyingoperation has commenced, the mechanical stability of the cast part isassured by a solidified metal layer that forms along the walls of thecasting mold.

The material of the casting mold is then supposed to change under theinfluence of the heat released by the metal such that it loses itsmechanical strength, i.e. the coherence between individual particles ofrefractory material is lost. In the ideal case, casting molds and coresbreak down again to form a fine sand that can be removed easily from thecast part and have correspondingly favorable breakdown properties.

Inorganic binders have long been known, especially those based onwaterglasses. Three different methods in particular are available forcuring of the waterglasses, which may also be combined: (i) passage of agas, e.g. CO₂, air or a combination of the two; (ii) addition of liquidor solid curing agents, e.g. particular esters, and (iii) thermalcuring, for example in what is called a hotbox method or by microwavetreatment.

However, the use of inorganic binder systems is frequently associatedwith other typical disadvantages:

For instance, it is relatively common for foundry moldings produced frominorganic binders to have low strengths unless suitable special measuresare taken. This becomes particularly clearly apparent immediately afterthe removal of the core or casting mold or of the molding from the mold.The strengths at this time (“hot strength” or “immediate strength”) areparticularly important for the safe handling of the cores or forms onremoval from the mold. Also important is a high “cold strength” (i.e.the strength after complete curing of the core or of the casting mold),in order that the desired cast part can be produced with a minimum levelof casting defects.

Document EP 1 802 409 B1 discloses a molding material mixture forproducing casting molds for metal processing, at least comprising: arefractory mold base material, a waterglass-based binder, characterizedin that a proportion of a particulate synthetic amorphous silicondioxide has been added to the molding material mixture.

Document DE 10 2013 111 626 A1 discloses a molding material mixture forproduction of molds or cores, at least comprising: a refractory moldbase material, waterglass as binder, particulate amorphous silicondioxide and one or more pulverulent oxidic boron compounds. The documentadditionally discloses that the addition of boron compounds to themolding material mixture improves the moisture stability of the coresand molds produced therewith.

Document WO2014/202042A1 discloses a molding material mixture forproduction of casting molds and cores for metal processing, comprisingat least one refractory mold base material, particulate amorphous SiO₂,waterglass and lithium compounds. The document additionally disclosesthat the addition of lithium compounds to the molding material mixtureimproves the moisture stability of the moldings produced therewith.

Document DE 10 2012 104 934 A1 discloses a molding material mixture forproduction of casting molds for metal processing, at least comprising: arefractory mold base material, a waterglass-based binder and bariumsulfate.

Document DE 10 2012 113 073 A1 discloses a molding material mixture forproduction of forms and cores for metal processing, comprising at leasta) a refractory mold base material, b) an inorganic binder and c) atleast one particulate metal oxide, wherein the particulate metal oxidecomprises or consists of at least one aluminum oxide in the alpha phaseand/or at least one mixed aluminum/silicon oxide, excluding mixedaluminum/silicon oxides having sheet silicate structure.

Document DE 10 2012 113 074 A1 discloses a molding material mixture forproduction of forms and cores for metal processing, comprising at leastone refractory mold base material, an organic binder and at least oneparticulate mixed metal oxide. Oxides of aluminum and of zirconium areused in a specific manner.

Document DE 10 2017 107 531 A1 discloses a process for producing castingmolds, cores, and mold base materials regenerated therefrom. Particulatesheet silicates are used in a specific manner.

Document EP 2 104 580 B1 discloses a molding material mixture forproduction of casting molds for metal processing, at least comprising: arefractory mold base material; a waterglass-based binder; a proportionof a particulate metal oxide selected from the group of silicon dioxide,aluminum oxide, titanium oxide and zinc oxide. A carbohydrate has beenadded to the molding material mixture.

Document EP 2 097 192 B1 discloses a molding material mixture forproduction of casting molds for metal processing, at least comprising: arefractory mold base material; a waterglass-based binder; a proportionof a particulate metal oxide selected from the group of silicon dioxide,aluminum oxide, titanium oxide and zinc oxide. A proportion of aphosphorus compound has been added to the molding material mixture.

Document DE 10 2012 020 509 A1 discloses a molding material mixture forproduction of casting molds and cores for metal processing, comprisingat least: a refractory mold base material, an inorganic binder andparticulate amorphous SiO₂, producible by the thermal breakdown ofZrSiO₄ to give ZrO₂ and SiO₂.

Document DE 10 2012 020 510 A1 discloses a molding material mixture forproduction of casting molds and cores for metal processing, comprisingat least: a refractory mold base material, an inorganic binder andparticulate amorphous SiO₂, producible by the oxidation of metallicsilicon by means of an oxygenous gas.

Document DE 10 2012 020 511 A1 discloses a molding material mixture forproduction of casting molds and cores for metal processing, comprisingat least: a refractory mold base material, an inorganic binder andparticulate amorphous SiO₂, producible by melting crystalline quartz andrapid recooling.

Document DE 10 2012 020 073 A1 discloses a molding material mixture forproduction of casting molds and cores for metal processing, comprisingat least: a refractory mold base material, an inorganic binder andparticulate amorphous SiO₂, producible by the oxidation of metallicsilicon by means of an oxygenous gas.

Document WO 2009/056320 discloses a molding material mixture forproduction of casting molds for metal processing, at least comprising: arefractory mold base material; a waterglass-based binder; a proportionof a particulate metal oxide selected from the group of silicon dioxide,aluminum oxide, titanium oxide and zinc oxide. A proportion of at leastone surface-active substance has been added to the molding materialmixture.

The patent documents acknowledged above already disclose moldingmaterial mixtures comprising particulate amorphous SiO₂. It is alsoknown therefrom that, proceeding from particular base formulations, theaddition of selected additives influences the properties of moldingmaterial mixtures and moldings resulting therefrom.

In the foundry industry, there is a need to use binders and moldingmaterial mixtures comprising particulate amorphous silicon dioxide andoptionally further solid additives, but at the same time to minimize theinconvenience involved in individual dosage and mixing, which has todate additionally been associated in practice with health risksresulting from contamination of breathable air. At the same time, it isto be ensured that repeatedly produced binders and molding materialmixtures always have the same composition and always have the sameproduct properties.

In addition, there is a need to use substances even in gel or liquidform that do not have prolonged stability in waterglass as constituentsof corresponding binders and molding material mixtures without any needfor additional metering steps.

There is additionally a need to use various particulate substances eachhaving very different particle size distributions as additives formolding material mixtures without any need for additional metering stepsand without any resultant differences, for example, in the compositionsof the molding material mixtures formed depending on the fill levels inthe reservoir vessels for the particulate substances.

There is additionally a need to add solid and liquid additives formolding material mixtures to molding material mixtures in a fixedlydefined relative ratio to one another and by means of a single commonmetering step.

Very particularly, there is a need to be able to combine the knownpositive properties of additives for molding material mixtures withoutneeding additional metering steps for every component added and withouthaving to deal with additional problems with the storage of theadditives.

The present invention is defined in the claims and described in detailhereinafter.

The present invention relates, in its categories, to a process forproducing an article for use in the foundry industry, to a granularmaterial, to an apparatus for performance of a process, to a use ofparticulate amorphous silicon dioxide, and to a use of a granularmaterial. Embodiments, aspects or properties that are described inconnection with one of these categories or described as preferred areeach correspondingly or analogously applicable to the respective othercategories, and vice versa.

Unless stated otherwise, preferred aspects or embodiments of theinvention and their various categories can be combined with otheraspects or embodiments of the invention and their various categories,especially with other preferred aspects or embodiments. The combinationof respectively preferred aspects or embodiments with one another againresults in preferred aspects or embodiments of the invention.

In a primary aspect of the present invention, the above-specifiedobjects are achieved and problems are solved in whole or in part by aprocess for producing an article for use in the foundry industry

-   -   selected from the group consisting of        -   granular material for production of a pourable additive for            use as a constituent of an inorganic binder in the foundry            industry,        -   solid pourable additive for use as a constituent of an            inorganic binder in the foundry industry,        -   inorganic binder for use in the foundry industry,        -   molding material mixture comprising an inorganic binder for            use in the foundry industry,    -   and        -   moldings (especially cores, casting molds and feeders) for            use in the casting of metallic cast parts in the foundry            industry,    -   comprising the following steps for production of the article:        -   producing or providing particulate amorphous silicon dioxide            comprising silicon dioxide in a proportion of at least 80%            by weight, preferably in a proportion of at least 90% by            weight, based on the total mass of the particulate amorphous            silicon dioxide,        -   combining the particles of the particulate amorphous silicon            dioxide in an enlargement step to give grains, so as to            result in a granular material comprising a multitude of            individual grains each comprising combined particles and            each comprising a proportion of at least 30% by weight,            preferably at least 40% by weight, more preferably at least            50% by weight, of particulate amorphous silicon dioxide,            based on the mass of the respective grain, where the average            grain diameter of the granular material is greater than 0.2            mm, determined by sieving.

The granular material, the solid pourable additive, the inorganic binderand the molding material mixture are each intermediates as producedsuccessively (in the specified sequence) in the production of a castingmold or core. Each of these intermediates may be individually stored orelse transported.

The term “granular material” is thus understood in the context of theabove definition to mean the entirety of a multitude of grains asdefined above.

The grains here are the product of an enlargement step performed asplanned, and contain particulate amorphous silicon dioxide (andoptionally further substances). The grains are thus in each case acomposite, for example an agglomerate or aggregate.

The term “particulate” preferably refers to the particles of a solidpowder (including dusts) that is preferably pourable and hence alsosievable.

Particulate amorphous silicon dioxide used may be either syntheticallyproduced types (for example as defined in the prior art acknowledged atthe outset) or naturally occurring types. The latter are known, forexample, from DE 10 2007 045 649, but they are not preferred since theyfrequently contain not inconsiderable crystalline components and aretherefore classified as carcinogenic.

The “particulate amorphous silicon dioxide comprising silicon dioxide ina proportion of at least 80% by weight, based on the total mass of theparticulate amorphous silicon dioxide” is preferably a particulatesynthetic amorphous silicon dioxide. According to the origin orpreparation process, natural and/or synthetic amorphous silicon dioxidecontains up to 50% by weight of secondary constituents, i.e. crystallinesilicon dioxide and/or non-silicon dioxide substances. Thus,commercially available (synthetic or natural) “particulate amorphoussilicon dioxide”, aside from silicon dioxide, typically containsproportions of one or more further inorganic oxides and of unavoidableimpurities. In the context of the present invention, preference is givento synthetic amorphous silicon dioxide containing secondary constituentsin a proportion of less than 30% by weight and/or silicon dioxide in aproportion of at least 80% by weight, very particular preference toparticulate synthetic amorphous silicon dioxide containing secondaryconstituents in a proportion of less than 20% by weight and/or silicondioxide in a proportion of at least 90% by weight, based in each case onthe total mass of the particulate amorphous silicon dioxide.

Typically, and preferably in some cases, the particulate amorphoussilicon dioxide produced or provided comprises particles in the form ofdust.

The proportion of particulate amorphous silicon dioxide in the grains ofthe granular material may (after appropriate sample processing,especially after sieving according to VDG-Merkblatt P 27, see below) bedetermined or confirmed, for example, by means of x-ray fluorescenceanalysis to DIN EN ISO 12677, DIN 51001, optionally in combination withoptical and/or spectroscopic methods and/or wet-chemical methods; theperson skilled in the art will preferably choose a suitable method ofdetermination with knowledge of the materials used in the process.

The particulate amorphous silicon dioxide produced or providedpreferably comprises particles having a size of less than 20 μm, morepreferably particles having a size of 0.1 μm to 5 μm, most preferablyparticles having a size of 0.1 μm to 1.5 μm, determined by scanningelectron microscopy (SEM) or laser diffraction.

Preference is given in many cases to a process wherein, for theresulting granular material, the index for the evolution of dust by therotation method is lower than that of the particulate amorphous silicondioxide produced or provided, preferably at least 15% lower, morepreferably at least 25% lower, most preferably at least 40% lower, ineach case preferably determined to DIN 55992-1 (date: June 2006), TypeI, Rotating drum principle (for example using a Heubach dustmeter).

What is meant by “synthetically produced” particulate amorphous silicondioxide in the context of the present text is that the amorphous silicondioxide is

-   -   the target product of a planned chemical reaction process for        industrial synthesis of amorphous silicon dioxide        or    -   a by-product of a planned chemical reaction process for        industrial synthesis of a target product that is not amorphous        silicon dioxide.

One example of a reaction process with amorphous silicon dioxide as itstarget product is the flame hydrolysis of silicon tetrachloride. Theamorphous SiO₂ (“silicon dioxide”) produced by this process is alsoreferred to as “pyrogenic SiO₂” (“pyrogenic silicon dioxide”) or aspyrogenic silica or as fumed silica (CAS RN 112945-52-5).

One example of a reaction process in which amorphous silicon dioxide isformed as a by-product is the reduction of quartz with coke, forexample, in an arc furnace for production of silicon or ferrosilicon astarget product. The amorphous SiO₂ (“silicon dioxide”) thus produced isalso referred to as silica dust, silicon dioxide dust or SiO₂ fumecondensate or as “silica fume” or microsilica (CAS RN 69012-64-2).

A further reaction process in which amorphous silicon dioxide issynthetically produced is the thermal breakdown of ZrSiO₄ in an arcfurnace to give ZrO₂ and SiO₂.

The literature frequently refers to amorphous silicon dioxide formed byflame hydrolysis of silicon tetrachloride, to amorphous silicon dioxideformed as a by-product in the reduction of quartz with coke, forexample, in the arc furnace and to amorphous silicon dioxide formed bythermal breakdown of ZrSiO₄ as “pyrogenic SiO₂” (“pyrogenic silicondioxide”) or as pyrogenic silica. This terminology is also employed inthe context of the present application.

In the context of the present invention, pyrogenic particulate amorphoussilicon dioxide to be used with particular preference in the context ofthe present invention includes those types of particulate amorphoussilicon dioxide that are identified by CAS RN 69012-64-2 and CAS RN112945-52-5. These types of pyrogenic particulate amorphous silicondioxide that are to be used with particular preference in accordancewith the invention can be produced in a manner known per se, especiallyby reduction of quartz with carbon (e.g. coke) in an arc furnace withsubsequent oxidation to silicon dioxide (preferably in the production offerrosilicon and silicon). Likewise particularly preferred is SiO₂prepared by thermal breakdown of ZrSiO₄ to give ZrO₂ from ZrSiO₄, andSiO₂ obtained by flame hydrolysis of silicon tetrachloride.

Particulate amorphous silicon dioxide of the type produced by reductionof quartz with carbon (e.g. coke) in an arc (in the production offerrosilicon and silicon) contains carbon. Particulate amorphous silicondioxide of the type produced by thermal breakdown of ZrSiO₄ containsoxidic zirconium compounds.

Particulate synthetic amorphous silicon dioxide producible by oxidationof metallic silicon by means of an oxygenous gas and particulatesynthetic amorphous silicon dioxide producible by quenching a silicondioxide melt are very pure SiO₂ having only a very small number ofunavoidable impurities.

Most preferably, the pyrogenic particulate amorphous silicon dioxide tobe used with preference in accordance with the invention comprisesparticulate amorphous silicon dioxide of the type identified by CAS RN69012-64-2. This is preferably produced by the reduction of quartz withcarbon (e.g. coke) in an arc (for example in the production offerrosilicon and silicon), or is obtained as a by-product (silica fume)in the production of ferrosilicon and silicon. Likewise veryparticularly preferred is SiO₂ prepared by thermal breakdown of ZrSiO₄to give ZrO₂ from ZrSiO₄. Particulate amorphous silicon dioxide of thesetypes is also referred to as “microsilica” in the specialist field.

The “CAS RN” stands here for the CAS registry number and CAS registernumber (CAS=Chemical Abstracts Service).

Various methods are suitable for combining of the particles of theparticulate amorphous silicon dioxide (and optionally furthersubstances) in an enlargement step to give grains, so as to result in agranular material comprising a multitude of individual grains. Examplesof suitable methods include pelletizing, briqueting, tableting,granulating, agglomerating, extruding and others.

The “Handbuch derAgglomerationstechnik” [Handbook of AgglomerationTechnology] by the author Gerald Heinze (WILEY-VCH Verlag GmbH, 2000,ISBN: 3-527-29788-X) discloses processes and products from the field ofagglomeration technology.

EP 1 602 425 A1 discloses granular materials obtainable from silicondioxide powder having a content of at least 90% amorphous SiO₂ bygranulation, especially by pelletization with addition of water andsubsequent drying.

A “molding material mixture” in the context of the invention definedabove comprises a mold base material as one of multiple constituents.The mold base material here is preferably a refractory mold basematerial.

In the present text, in accordance with the customary understanding ofthe person skilled in the art, “refractory” masses, materials andminerals refer to those that can at least briefly withstand the thermalstress in the course of casting or solidifying of an iron melt, usuallycast iron. Suitable (refractory) mold base materials are natural andsynthetic mold base materials, for example quartz sand, zircon sand orchrome ore sand, olivine, vermiculite, bauxite or fireclay, and mixturesthereof.

The juncture of addition of the additive to the further constituents inthe production of the molding material mixture or of the moldingmaterial mixture provided with the additive is arbitrary and can bechosen freely. For example, the additive can be added last to theotherwise finished molding material mixture or can first be premixedwith one or more of the constituents mentioned before one or morefurther constituents are finally mixed into the molding materialmixture.

A solid pourable additive is understood to mean an additive for moldingmaterial mixtures in the form of a bitty aggregate in a pourable formand amount, with the individual piece of this aggregate having a size ofless than 0.2 mm, determined by sieving.

An “inorganic binder” in the context of the above definition of theinvention is typically a multicomponent binder system comprisingadditives comprising at least particulate amorphous silicon dioxide, anda solution or dispersion comprising waterglass. Said constituents arepresent here as two or more spatially separate components or as amixture. “Inorganic binders” may, as well as particulate amorphoussilicon dioxide, also contain further particulate materials and/orfurther materials in liquid or gel form, each as part of a mixtureand/or as spatially separate components.

Mixture constituents that would be unacceptable as an individualcomponent in a foundry process (for example respirable crystalline SiO₂,classified as carcinogenic), in some cases, albeit not preferably, areused in accordance with the invention in the granular material sincerelease in dust form can be effectively prevented or reduced to aconsiderable degree.

What is meant by the term “combining” is the combining of the particlesof the particulate amorphous silicon dioxide with one another andoptionally also with further constituents (see below).

The process of the invention is suitable for the production of allmoldings customary for metal casting, i.e., for example, of cores,casting molds and feeders. It is also particularly advantageouslypossible to produce moldings having sections with very thin walls. It islikewise particularly advantageously possible to produce moldings thatcombine a maximum relative molding weight (weight based on the volume ofa given body of predetermined geometry; in the case of cores, this isreferred to as core weight) with a particularly high one-hour strength.

The present invention, with its various aspects, especially andpreferably relates to a process (as described above, preferably asidentified above as preferred) for producing an article for use in thefoundry industry, selected from the group consisting of

-   -   solid pourable additive for use as a constituent of an inorganic        binder in the foundry industry,    -   inorganic binder for use in the foundry industry,    -   molding material mixture comprising an inorganic binder for use        in the foundry industry,    -    and    -   moldings for use in the casting of metallic cast parts in the        foundry industry,    -    comprising the steps of:    -   producing a granular material by a process as described above,        preferably as identified above as preferred,    -   comminuting the grains of the granular material, so as to result        in a solid pourable additive.

The person skilled in the art is able to select from a multitude ofmethods for the comminution of the grains of the granular material, soas to result in a solid pourable additive. The comminuting preferablycomprises grinding or crushing. But the granular material can also becomminuted in other ways.

In a preferred embodiment, the comminuting, preferably the grinding orcrushing, takes place in a closed apparatus, such that no significantamounts of dust and/or fine dust are released outside the apparatus andcontaminate the breathable air. In that case, preference is given tometering the resulting solid pourable additive into the furtherconstituents of the inorganic binder or molding material mixtures suchthat this also does not release any dust and/or fine dust.

The invention especially and preferably relates to a process (asdescribed above, preferably as identified above as preferred) forproducing an article for use in the foundry industry,

-   -   selected from the group consisting of        -   inorganic binder for use in the foundry industry,        -   molding material mixture comprising an inorganic binder for            use in the foundry industry,    -   and        -   moldings for use in the casting of metallic cast parts in            the foundry industry,    -   (i) comprising the steps of:        -   producing the solid pourable additive by an above-defined            process of the invention (preferably in a configuration            identified as preferred),        -   contacting the solid pourable additive produced with            waterglass or suspending the solid pourable additive            produced in waterglass,    -   or    -   (ii) comprising the steps of:        -   producing a granular material by an above-defined process of            the invention        -   contacting the granular material produced with waterglass,            in the presence or absence of refractory mold base material,            and comminuting the grains of the granular material at the            same time or thereafter.

Waterglass may be produced, for example, by dissolving vitreous sodiumand potassium silicates in water in an autoclave at elevated temperatureor from lithium silicates in a hydrothermal process. According to theinvention, it is possible to use waterglass containing one, two or moreof the alkali metal ions mentioned. The proportion of waterglass in amolding material mixture in the context of the present invention ispreferably in the range from 0.6% to 3% by weight.

The contacting of the solid pourable additive produced with waterglassor suspending of the solid pourable additive produced in waterglass thattakes place in variant (i) requires the granular material producedbeforehand first to have been processed by comminution, preferably bygrinding or crushing, to give a solid pourable additive. Thus, solidpourable additive produced from the granular material comes into contactwith the waterglass, or is suspended therein. More preferably, thecontacting of the solid pourable additive produced with waterglass takesplace in such a way that refractory mold base material is initiallycharged, then the solid pourable additive is added and, finally,waterglass is added, and, at the same time or thereafter, mixing allcomponents used until they have preferably been blended homogeneouslywith one another. In less preferred embodiments, the sequence can alsobe altered, such that, for example, the refractory mold base material isinitially charged, then the waterglass is added and only then is thesolid pourable additive added, and, at the same time and/or thereafter,all the components used are mixed until they have been blendedhomogeneously with one another. In a further embodiment, the solidpourable additive is blended with the waterglass to give a suspensionand then this suspension is added to the initial charge of refractorymold base material, and, at the same time and thereafter, all componentsused are mixed until they have been blended homogeneously with oneanother.

The contacting of the granular material produced with waterglass in thepresence or absence of refractory mold base material that takes place invariant (ii) and, at the same time or thereafter, comminuting of thegrains of the granular material means that (initially uncomminuted)grains of the granular material are contacted with the waterglass. Theperson skilled in the art, according to the circumstances of theindividual case, will be able to achieve comminution of the grains byadjusting the studding conditions to the demands of the individual casein the contacting and blending of the granular material produced withwaterglass. The person skilled in the art will likewise be able,according to the circumstances of the individual case, by appropriateadjustment of the stirring conditions, to blend the granular materialwith the waterglass in such a way that there is essentially nocomminution of the individual grains of the granular material. In bothcases, the contacting and blending of the granular material producedwith waterglass can take place in the presence or absence of refractorymold base material. If the contacting of the granular material producedwith waterglass takes place in the presence of refractory mold basematerial, it is preferable that blending takes place on contacting (orimmediately thereafter) and this blending comminutes the grains of thegranular material.

In each of variants (i) and (ii), it is possible to use waterglass inthe form of a mixture with one or more additives, for example a mixturecomprising waterglass and one or more surfactants.

In a departure from the prior art, in the process of the invention,there is no direct use of particulate amorphous SiO₂ for production ofthe inorganic binder or of the molding material mixture, but ratherexclusively of the granular material produced or the solid pourableadditive produced therefrom.

The effects and advantages set out above in connection with the processof the invention are achieved here to a particular degree.

The invention relates especially and preferably to a process of theinvention (as described above, preferably as identified above aspreferred) for producing a molding material mixture comprisingrefractory mold base material and an inorganic binder comprisingwaterglass and particulate amorphous silicon dioxide for use in thefoundry industry,

-   -   comprising the steps of:        -   producing an inorganic binder by an above-defined process of            the invention (preferably in a configuration identified as            preferred),    -   and        -   (i) at the same time mixing the constituents used for            production of the inorganic binder with a refractory mold            base material    -   and/or        -   (ii) thereafter mixing the inorganic binder produced with a            refractory mold base material.

The molding material mixture can be produced by mixing the individualconstituents used for production of the inorganic binder with oneanother in the presence of a refractory mold base material to give themolding material mixture. The molding material mixture can likewise beproduced by first producing the inorganic binder by mixing theconstituents of the inorganic binder and mixing the ready-producedinorganic binder with a refractory mold base material to give themolding material mixture. According to the requirements of theindividual case, one or both variants in each case or a combination ofthe two variants may be preferred.

The refractory mold base material preferably accounts for more than 80%by weight, preferably more than 90% by weight, more preferably more than95% by weight, of the total mass of the molding material mixture. Therefractory mold base material to be used in accordance with theinvention is preferably in particulate form. It is preferablyfree-flowing.

The refractory mold base material preferably has an AFS grain finenessnumber in the range from 30 to 100. The AFS grain fineness number isdetermined here according to VDG-Merkblatt (information sheet from the“Verein deutscher GieBereifachleute” [Society of German FoundryExperts]) P 34 of October 1999, point 5.2. The AFS grain fineness numberis specified therein by the formula

${{AFS}\mspace{14mu}{grain}\mspace{14mu}{fineness}\mspace{14mu}{number}} = \frac{\sum{g_{i} \times M\; 3_{i}}}{g}$

Preference is given to a process of the invention (as described above,preferably as identified above as preferred), wherein, in the step ofcombining the particles of the particulate amorphous silicon dioxide inan enlargement step to give grains, so as to result in a granularmaterial comprising a multitude of individual grains each comprisingcombined particles and each comprising a proportion of at least 30% byweight, preferably at least 40% by weight, more preferably at least 50%by weight, of particulate amorphous silicon dioxide, based on the massof the respective grain, the average grain diameter of the (resulting)granular material is greater than 0.5 mm, preferably greater than 1 mm,determined by sieving.

This preferred process of the invention thus leads to granular materialsin which the grains have an average grain diameter of greater than 0.5mm, preferably an average grain diameter of greater than 1 mm(determined by sieving), and each comprise a proportion of at least 30%by weight, preferably at least 40% by weight, more preferably at least50% by weight, of particulate amorphous silicon dioxide (as statedabove). The granular materials produced by this method have particularlyadvantageous combinations of the following properties: homogeneouscomposition, high bulk density, good flowability, good conveyability,good meterability, low dust level, avoidance of separation phenomena,comminutability, high molding weight of the moldings producible with usethereof, elevated moisture stability (moisture resistance) of themoldings producible with use thereof.

Preference is given to a process of the invention (as described above,preferably as identified above as preferred), wherein the particulateamorphous silicon dioxide comprising silicon dioxide in a proportion ofat least 80% by weight, based on the total mass of the particulateamorphous silicon dioxide, consists wholly or partly of particulatesynthetic amorphous silicon dioxide.

According to the requirements of the individual case, it is particularlyadvantageous when the particulate amorphous silicon dioxide (comprisingsilicon dioxide in a proportion of at least 80% by weight, based on thetotal mass of the particulate amorphous silicon dioxide) consists whollyor only partly of particulate synthetic amorphous silicon dioxide. Withthe regularly preferred use of synthetic amorphous silicon dioxide, itis possible to achieve particularly advantageous combinations ofproperties of moldings obtainable therefrom in uniform, predictablequality.

Preference is given to a process of the invention (as described above,preferably as identified above as preferred) wherein the proportion ofsilicon dioxide in the granular material as a whole, determined by meansof x-ray fluorescence analysis, and the proportion of silicon dioxide inat least 90% of the grains of the granular material having a graindiameter greater than 1 mm, preferably greater than 0.5 mm, morepreferably greater than 0.2 mm, in each case determined by means ofsieving and subsequent x-ray fluorescence analysis, differs by not morethan 30%, preferably differs by not more than 20%, more preferablydiffers by not more than 10%, based on the proportion of silicon dioxidein the granular material as a whole.

The proportion of silicon dioxide both in the granular material as awhole and in the individual grains of the granular material isascertained by means of x-ray fluorescence analysis to DIN EN ISO 12677,DIN 51001. The (average) grain diameter is determined by sievingaccording to VDG-Merkblatt (i.e. information sheet from the “Vereinsdeutscher GieBereifachleute”) P 27 of October 1999, point 4.3, whichspecifies the use of test sieves according to DIN ISO 3310. What ismeant by the fact that the proportion of silicon dioxide in the granularmaterial as a whole (determined by x-ray fluorescence analysis) and theproportion of silicon dioxide (determined by x-ray fluorescenceanalysis) in at least 90% of the individual grains of the granularmaterial having a grain diameter greater than 1 mm (determined bysieving), preferably greater than 0.5 mm (determined by sieving), morepreferably greater than 0.2 mm (determined by sieving), differ by notmore than 30%, preferably by not more than 20%, more preferably by notmore than 10% (based on the proportion of silicon dioxide in thegranular material as a whole), is that these granule grains of this(minimum) size in their composition are good representatives of theoverall composition of the granular material and hence of the entiretyof the material used. For each of the sizes mentioned (1 mm, 0.5 mm, 0.2mm), according to the individual case, it is also possible for any ofthe maximum differences specified (30%, 20%, 10%) to be relevant andadvantageous. Thus, according to the requirements of the individualcase, any resultant combination of size and maximum difference ispreferred.

Preference is given to a process of the invention (as described above,preferably as identified above as preferred), wherein, in theenlargement step, the particles of the particulate amorphous silicondioxide are mixed and/or contacted with one, two or more furthermaterials independently selected from the group consisting of:

-   -   liquids, including substances in gel form, preferably liquid        wetting agents and/or suspension media, preferably water,    -   particulate materials, preferably particulate inorganic        materials, preferably selected from the group consisting of        oxides of aluminum, preferably aluminum oxide in the alpha        phase, bauxite, oxides of zirconium, preferably zirconium(IV)        oxide, mixed aluminum/silicon oxides, zinc oxide, barium        sulfate, phosphorus compounds, sheet silicates, graphite, carbon        black, glass beads, oxides of magnesium, borosilicates, ceramic        hollow beads, oxidic boron compounds, preferably pulverulent        oxidic boron compounds, and mixtures thereof,    -   water-soluble materials,    -   alkali metal hydroxides,    -   surfactants,    -   film formers,    -   rheological additives (thickeners, suspension aids),    -   hydrophobizing agents, preferably organosilicon compounds,        silanes, silicones and siloxanes, waxes, paraffins, metal soaps,    -    and    -   carbohydrates.

The particulate amorphous silicon dioxide is preferably mixed and/orcontacted in the enlargement step with one, two or more furthermaterials (that are not themselves particulate amorphous silicondioxide). The selection of the one, two or more further materials withwhich the particulate amorphous silicon dioxide is mixed and/orcontacted in the enlargement step is made independently from the abovelist, meaning that the selection of a first material has no effect onthe selection of any subsequent material(s).

The surfactant(s) is/are preferably independently selected from thegroup consisting of or comprising: oleyl sulfate, stearyl sulfate,palmityl sulfate, myristyl sulfate, lauryl sulfate, decyl sulfate, octylsulfate, 2-ethylhexyl sulfate, 2-ethyloctyl sulfate, 2-ethyldecylsulfate, palmitoleyl sulfate, linolyl sulfate, lauryl sulfonate,2-ethyldecyl sulfonate, palmityl sulfonate, stearyl sulfonate,2-ethylstearyl sulfonate, linolyl sulfonate, hexyl phosphate,2-ethylhexyl phosphate, capryl phosphate, lauryl phosphate, myristylphosphate, palmityl phosphate, palmitoleyl phosphate, oleyl phosphate,stearyl phosphate, poly(ethane-1,2-diyl)phenol hydroxyphosphate,poly(ethane-1,2-diyl)stearyl phosphate, poly(ethane-1,2-diyl)oleylphosphate, polycarboxylate ethers in water (e.g. Melpers 0030, fromBASF), modified polyacrylate in water (e.g. Melpers VP 4547/240 L, fromBASF), 2-ethylhexyl sulfate in water (e.g. Texapon EHS, from Cognis),polyglucoside in water (e.g. Glukopon 225 DK, from Cognis), sodiumoctylsulfate in water (e.g. Texapon 842, from Lakeland), modifiedcarboxylate ethers (e.g. Castament ES 60, solid-state, from BASF).

The film former(s) is/are preferably independently selected from thegroup consisting of or comprising: polyvinylalcohol and acrylic acid.

The rheological additive(s) (thickeners, suspension aids) is/arepreferably independently selected from the group consisting of orcomprising:

-   -   swellable clays, preferably sodium bentonite or        attapulgite/palygorskite,    -   swellable polymers, preferably cellulose derivatives, especially        carboxymethyl, methyl, ethyl, hydroxyethyl and hydroxypropyl        cellulose, plant mucilages, polyvinylpyrrolidone, pectin,        gelatin, agar-agar, polypeptides and/or alginates.

The hydrophobizing agent(s) is/are preferably independently selectedfrom the group consisting of or comprising: preferably organosiliconcompounds, silanes, silanols, preferably trimethylsilanol, silicones andsiloxanes, preferably polydimethylsiloxane, waxes, paraffins, metalsoaps.

The materials listed above are those that are preferred in the contextof the present invention. Further materials may likewise be usedaccording to the requirements of the individual case.

The aforementioned materials may thus also be used in the process of theinvention without any need for an additional dosage step or additionalstorage vessels in the foundry. It is also possible to introduce thosecomponents, preferably including those liquid components (includingthose in gel form) that do not have prolonged stability in waterglass,into a molding material mixture produced in accordance with theinvention without an additional dosage step, in that they areincorporated into the granules formed in the enlargement step.

The term “carbohydrate” in the context of this text is understood tomean aldoses (polyhydroxyaldehydes) and ketoses (polyhydroxyketones),and also higher molecular weight compounds that can be converted to suchcompounds by hydrolysis. Carbohydrates that are used in the context ofthe present invention are oligomers and polymers having a chain lengthof n>2. The invention also relates to a process of the invention (asdescribed above, preferably as identified above as preferred), whereingrains of the granular material resulting from the enlargement step,preferably at least 90% of the grains of the granular material having aparticle diameter greater than 1 mm, preferably greater than 0.5 mm,more preferably greater than 0.2 mm, in each case determined by sieving,

-   -   (i) comprise particulate amorphous silicon dioxide and one, two,        more than two or all of the further solid materials present in        the enlargement step    -    and/or    -   (ii) comprise particulate amorphous silicon dioxide and one, two        or more further materials independently selected from the group        consisting of:        -   particulate materials, preferably particulate inorganic            materials, preferably selected from the group consisting of            oxides of aluminum, preferably aluminum oxide in the alpha            phase, bauxite, oxides of zirconium, preferably            zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc            oxide, barium sulfate, phosphorus compounds, sheet            silicates, graphite, carbon black, glass beads, oxides of            magnesium, borosilicates, ceramic hollow beads, oxidic boron            compounds, preferably pulverulent oxidic boron compounds,            and mixtures thereof,        -   water-soluble materials,        -   alkali metal hydroxides,        -   surfactants,        -   film formers,        -   rheological additives (thickeners, suspension aids),        -   hydrophobizing agents, preferably organosilicon compounds,            silanes, silicones and siloxanes, waxes, paraffins, metal            soaps,    -   and        -   carbohydrates.

The proportion/presence of silicon dioxide in the individual grains ofthe granular material is ascertained by means of x-ray fluorescenceanalysis to DIN EN ISO 12677, DIN 51001. The grain diameter isdetermined by sieving according to VDG-Merkblatt (i.e. information sheetfrom the “Vereins deutscher GieBereifachleute”) P 27 of October 1999,point 4.3, which specifies the use of test sieves according to DIN ISO3310. The presence of the one, two, more than two or all further solidmaterials present in the enlargement step in the grains of the granularmaterial may (especially after sieving according to VDG-Merkblatt P 27,see above) likewise be determined or confirmed, for example, by means ofx-ray fluorescence analysis according to DIN EN ISO 12677, DIN 51001,optionally in combination with optical and/or spectroscopic methodsand/or wet-chemical methods. The person skilled in the art will choose asuitable method of determination, preferably with knowledge of thematerials used in the process.

The fact that grains of the granular material, preferably at least 90%of the grains of the granular material having a grain diameter greaterthan 0.2 mm, preferably greater than 0.5 mm, more preferably greaterthan 1 mm (in each case determined by sieving), comprise particulateamorphous silicon dioxide and one, two or more than two or all of theother solid materials present in the enlargement step means that one,two or more than two or all of the other solid materials present in theenlargement step are part of the resulting granular material, preferablypart of at least 90% of the grains of the granular material (having agrain diameter greater than 0.2 mm, preferably greater than 0.5 mm, morepreferably greater than 1 mm). Thus, the one, two or more than two orall of the other solid materials present in the enlargement step arepreferably part of the granular material; more preferably, they aredistributed sufficiently uniformly within the granular material thatthey are present in at least 90% of the grains of the granular materialhaving a grain diameter of greater than 1 mm, preferably greater than0.5 mm, more preferably greater than 0.2 mm (in each case determined bysieving).

The one, two, more than two or all of the other materials present in theenlargement step in addition to the particulate amorphous silicondioxide are selected independently from one another. Each of thepossible resultant combinations, according to the requirements of theindividual case, leads to particularly advantageous properties orcombinations of properties of the molded articles producible therefrom.

Preference is given to a process of the invention (as described above,preferably as identified above as preferred), wherein

-   -   the producing of particulate amorphous silicon dioxide        comprising silicon dioxide in a proportion of at least 80% by        weight, based on the total mass of the particulate amorphous        silicon dioxide, comprises the step of:        -   mixing two or more different types of particulate amorphous            silicon dioxide, where the two or more types differ by their            particle size distribution, preferably determined by laser            scattering, for example by the median value of their            particle size distribution, determined by laser scattering,            and/or their chemical composition.

It is possible here for both types of particulate amorphous silicondioxide to be selected such that they are chemically different andadditionally have different particle size distribution. Alternatively,both types may be selected such that they merely have different particlesize distributions with identical chemical composition. It isadditionally possible for both types of particulate amorphous silicondioxide to be selected such that they are chemically different but havethe same particle size distribution.

The median value of a particle size distribution is understood to meanthe value at which half of the particle population examined has asmaller size than that value, while the other half of the particlepopulation examined has a greater size than that value. This value ispreferably ascertained as described further down in example 1 for acommercially available material.

What is meant (here and hereinafter) by “determined by means of lightscattering” is that a sample of the particulate material to beexamined—if required—is pretreated analogously to the method of example1 (see below) and the particle size distribution of the material thuspretreated is then determined by means of laser scattering as in example1 (see below).

The invention also relates to a process of the invention (as justdescribed, preferably as identified above as preferred),

-   -   (i)—wherein a first type of particulate amorphous silicon        dioxide has a particle size distribution having a median in the        range from 0.1 to 0.4 μm, determined by laser scattering,        -   and        -   wherein a further type of particulate amorphous silicon            dioxide has a particle size distribution having a median in            the range from 0.7 to 1.5 μm, determined by laser            scattering,    -   and/or    -   (ii)—wherein one, two, more than two or all of the different        types of particulate amorphous silicon dioxide is selected or        are independently selected from the group (of chemically        different materials) consisting of        -   particulate synthetic amorphous silicon dioxide containing            silicon dioxide in a proportion of at least 80% by weight,            based on the total mass of the particulate synthetic            amorphous silicon dioxide, and at least carbon as secondary            constituent, preferably producible by reducing quartz in an            arc furnace;        -   particulate synthetic amorphous silicon dioxide comprising            oxidic zirconium as secondary constituent and preferably            producible by thermal breakdown of ZrSiO₄        -   particulate synthetic amorphous silicon dioxide producible            by oxidizing metallic silicon by means of an oxygenous gas;        -   particulate synthetic amorphous silicon dioxide producible            by quenching a silicon dioxide melt.

Preference is given to a process of the invention (as described above,preferably as identified above as preferred) wherein at least 90% of thegrains of the granular material having a particle diameter greater than0.2 mm, preferably greater than 0.5 mm, more preferably greater than 1mm, in each case determined by sieving, comprise both or at least two ofthe different types of particulate amorphous silicon dioxide, preferablydetermined or confirmed (after appropriate sample processing, especiallyby sieving according to VDG-Merkblatt P 27, see below), for example bymeans of x-ray fluorescence analysis according to DIN EN ISO 12677, DIN51001, optionally in combination with optical and/or spectroscopicmethods and/or wet-chemical methods; the person skilled in the art willchoose a suitable method of determination, preferably with knowledge ofthe materials used in the process.

Preference is given to a process of the invention (as described above,preferably as identified above as preferred), wherein the enlargementstep comprises one or more measures independently selected from thegroup consisting of:

-   -   granulating    -   extruding    -    and    -   agglomerating, preferably press agglomerating.

Further suitable processes for performing the enlargement step are knownfrom the prior art and may likewise be used in accordance with theinvention alternatively or additionally, i.e., for example, pelletizing,briquetting, tableting and others. Reference is made to the aboveremarks.

The invention also relates to a granular material having an averagegrain diameter greater than 0.2 mm, determined by sieving, forproduction of a pourable additive for use as a constituent of aninorganic binder in the foundry industry, comprising (preferablysynthetic) particulate amorphous silicon dioxide,

-   -   (a) wherein the granular material additionally comprises        -   one, two or more further materials independently selected            from the group consisting of:            -   particulate materials, preferably particulate inorganic                materials, preferably selected from the group consisting                of oxides of aluminum, preferably aluminum oxide in the                alpha phase, bauxite, oxides of zirconium, preferably                zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc                oxide, barium sulfate, phosphorus compounds, sheet                silicates, graphite, carbon black, glass beads, oxides                of magnesium, borosilicates, ceramic hollow beads,                oxidic boron compounds, preferably pulverulent oxidic                boron compounds, and mixtures thereof,            -   water-soluble materials,            -   alkali metal hydroxides,            -   surfactants,            -   film formers,            -   hydrophobizing agents, preferably organosilicon                compounds, silanes, silicones and siloxanes, waxes,                paraffins, metal soaps,        -   and            -   carbohydrates,        -   wherein at least 90% of the grains of the granular material            having a grain diameter greater than 0.2 mm, preferably            greater than 0.5 mm, more preferably greater than 1 mm, in            each case determined by sieving, comprise particulate            amorphous silicon dioxide, and one, two or more of said            further materials,    -   and/or    -   (b) wherein the particulate amorphous silicon dioxide comprises        a proportion of at least 80% by weight of silicon dioxide, based        on the total mass of the particulate amorphous silicon dioxide,        preferably consisting wholly or partly of particulate synthetic        amorphous silicon dioxide,    -   and/or    -   (c) wherein the proportion of silicon dioxide in the granular        material as a whole, determined by means of x-ray fluorescence        analysis, and the proportion of silicon dioxide in at least 90%        of the grains of the granular material having a grain diameter        greater than 1 mm, in each case determined by means of sieving        and subsequent x-ray fluorescence analysis, differs by not more        than 30%, preferably differs by not more than 20%, more        preferably differs by not more than 10%, based on the proportion        of silicon dioxide in the granular material as a whole,    -   and/or    -   (d) wherein, in the granular material, the particulate amorphous        silicon dioxide comprises two or more different types of        particulate amorphous silicon dioxide, where the two or more        types differ by their chemical composition, preferably        determined or confirmed (especially after sieving according to        VDG-Merkblatt P 27, see above) by means of x-ray fluorescence        analysis according to DIN EN ISO 12677, DIN 51001 (optionally in        combination with optical and/or spectroscopic methods and/or        wet-chemical methods; the person skilled in the art will choose        a suitable method of determination, preferably with knowledge of        the materials used in the process),        -   wherein preferably one, two, more than two or all of the            different types of particulate amorphous silicon dioxide is            selected or are independently selected from the group            consisting of            -   particulate synthetic amorphous silicon dioxide                containing silicon dioxide in a proportion of at least                80% by weight, based on the total mass of the                particulate synthetic amorphous silicon dioxide, and at                least carbon as secondary constituent, preferably                producible by reducing quartz in an arc furnace;            -   particulate synthetic amorphous silicon dioxide                comprising oxidic zirconium as secondary constituent and                preferably producible by thermal breakdown of ZrSiO₄            -   particulate synthetic amorphous silicon dioxide                producible by oxidizing metallic silicon by means of an                oxygenous gas;            -   particulate synthetic amorphous silicon dioxide                producible by quenching a silicon dioxide melt    -   and/or    -   (e) wherein the granular material is producible by a process as        described above, preferably as identified above as preferred.

The granular material thus defined (i.e. the entirety of specificgrains, see above) has particularly advantageous combinations of thefollowing properties: homogeneous composition, high bulk density, lowdust level, good flowability, good conveyability, good meterability, lowdust level, avoidance of separation phenomena, comminutability, highmolding weight of the moldings producible with use thereof, elevatedmoisture stability (moisture resistance) of the moldings producible withuse thereof.

Configurations (a) and (e) are of particularly high economic relevanceand therefore preferred in many cases.

The invention also relates to a kit comprising, as spatially separatecomponent, a granular material (as described above, preferably asidentified above as preferred).

The invention also relates to a kit for production of an inorganicbinder (as described above, preferably as identified above aspreferred), more preferably a binder comprising and/or consisting of aninorganic multicomponent binder system, at least comprising, ascomponents in a mutually spatially separate arrangement,

-   -   a granular material (as described above, preferably as        identified above as preferred),    -    and    -   a solution or dispersion comprising waterglass.

The kit of the invention is particularly suitable for performance ofprocesses of the invention by which the successor products of thegranular material are produced (binder; molding material mixture;molding).

The effects and advantages set out above in connection with processes ofthe invention and granular material of the invention are achieved whenthe kit of the invention is used.

The invention also relates to an apparatus for performance of a processof the invention (as described above, preferably as identified above aspreferred), comprising

-   -   a reservoir vessel containing particulate amorphous silicon        dioxide, comprising silicon dioxide in a proportion of at least        80% by weight, based on the total mass of the particulate        amorphous silicon dioxide,    -   a mixing or contacting device for mixing or contacting the        particulate amorphous silicon dioxide with one, two or more        further materials,    -   a device for granulating, extruding and/or agglomerating the        particulate amorphous silicon dioxide that has been mixed or        contacted with one, two or more further materials.

The apparatus of the invention is particularly suitable for performanceof processes of the invention and for production of granular material ofthe invention.

The effects and advantages set out above in connection with processes ofthe invention and granular material of the invention may be achievedwhen the apparatus of the invention is used and established according torequirements of the individual case.

Preference is given to an apparatus of the invention (as describedabove, preferably as identified above as preferred), additionallycomprising one or more apparatus elements selected from the groupconsisting of

-   -   device for transferring particulate amorphous silicon dioxide        from the reservoir vessel into the mixing or contacting        apparatus,    -   one or more reservoir vessels containing liquid, preferably        liquid wetting agent and/or suspension medium, preferably water,    -   one or more reservoir vessels containing particulate material,        preferably particulate inorganic material, preferably selected        from the group consisting of oxides of aluminum, preferably        aluminum oxide in the alpha phase, bauxite, oxides of zirconium,        preferably zirconium(IV) oxide, mixed aluminum/silicon oxides,        zinc oxide, barium sulfate, phosphorus compounds, sheet        silicates, graphite, carbon black, glass beads, oxides of        magnesium, borosilicates, ceramic hollow beads, oxidic boron        compounds, preferably pulverulent oxidic boron compounds, and        mixtures thereof,    -   one or more reservoir vessels containing a water-soluble        material,    -   one or more reservoir vessels containing one or more        surfactants,    -   one or more reservoir vessels containing one or more        hydrophobizing agents,    -   one or more reservoir vessels containing one or more        carbohydrates.

According to the requirements of the individual case, the preferredapparatus (plant) is particularly advantageously suitable forperformance of a process of the invention and for production of agranular material of the invention.

Preference is given to an apparatus of the invention (as describedabove, preferably as identified above as preferred), additionallycomprising a device for dispensing or transporting granular materialproduced.

The invention also relates to the corresponding use (as described above,preferably as identified above as preferred) of (preferably synthetic)particulate amorphous silicon dioxide for production of or as aconstituent of a granular material.

The inventive use of particulate amorphous silicon dioxide forproduction of or as a constituent of a granular material, depending onthe particle size distribution of the particulate amorphous silicondioxide, with a molding material mixture produced therefrom produces amolding having a specific, preferably particularly high, relativemolding weight (in the case of cores: core weight). The inventive use ofparticulate amorphous silicon dioxide for production of or as aconstituent of a granular material, depending on the particle sizedistribution of the particulate amorphous silicon dioxide, with themolding material mixture produced therefrom produces a molding having aspecific, preferably particularly high, moisture stability.

The invention also relates to the use of a granular material (asdescribed above, preferably as identified above as in accordance withthe invention or as preferred) for production of a solid pourableadditive with homogenized grain composition for use as a constituent ofan inorganic binder in the foundry industry.

Preferred aspects of the present invention are specified hereinafter.

-   1. A process for producing a granular material for production of a    pourable additive for use as a constituent of an inorganic binder in    the foundry industry,    -   comprising the following steps for production of the granular        material:        -   producing or providing particulate amorphous silicon dioxide            comprising silicon dioxide in a proportion of at least 80%            by weight, preferably in a proportion of at least 90% by            weight, based on the total mass of the particulate amorphous            silicon dioxide,        -   combining the particles of the particulate amorphous silicon            dioxide in an enlargement step to give grains, so as to            result in a granular material comprising a multitude of            individual grains each comprising combined particles and            each comprising a proportion of at least 30% by weight,            preferably at least 40% by weight, more preferably at least            50% by weight, of particulate amorphous silicon dioxide,            based on the mass of the respective grain, where the average            grain diameter of the granular material is greater than 0.2            mm, determined by sieving,    -   wherein the particulate amorphous silicon dioxide produced or        provided preferably comprises particles having a size of less        than 20 μm, more preferably particles having a size of 0.1 μm to        5 μm, most preferably particles having a size of 0.1 μm to 1.5        μm, determined by scanning electron microscopy (SEM) or laser        diffraction.

The product of this process is said granular material.

-   2. A process for producing a solid pourable additive for use as a    constituent of an inorganic binder in the foundry industry,    -   comprising the following (and further) steps for production of        the solid pourable additive:        -   producing or providing particulate amorphous silicon dioxide            comprising silicon dioxide in a proportion of at least 80%            by weight, preferably in a proportion of at least 90% by            weight, based on the total mass of the particulate amorphous            silicon dioxide,        -   combining the particles of the particulate amorphous silicon            dioxide in an enlargement step to give grains, so as to            result in a granular material comprising a multitude of            individual grains each comprising combined particles and            each comprising a proportion of at least 30% by weight,            preferably at least 40% by weight, more preferably at least            50% by weight, of particulate amorphous silicon dioxide,            based on the mass of the respective grain, where the average            grain diameter of the granular material is greater than 0.2            mm, determined by sieving,    -   wherein the particulate amorphous silicon dioxide produced or        provided preferably comprises particles having a size of less        than 20 μm, more preferably particles having a size of 0.1 μm to        5 μm, most preferably particles having a size of 0.1 μm to 1.5        μm, determined by scanning electron microscopy (SEM) or laser        diffraction.-   3. A process for producing an inorganic binder for use in the    foundry industry    -   comprising the following (and further) steps for production of        the inorganic binder:        -   producing or providing particulate amorphous silicon dioxide            comprising silicon dioxide in a proportion of at least 80%            by weight, preferably in a proportion of at least 90% by            weight, based on the total mass of the particulate amorphous            silicon dioxide,        -   combining the particles of the particulate amorphous silicon            dioxide in an enlargement step to give grains, so as to            result in a granular material comprising a multitude of            individual grains each comprising combined particles and            each comprising a proportion of at least 30% by weight,            preferably at least 40% by weight, more preferably at least            50% by weight, of particulate amorphous silicon dioxide,            based on the mass of the respective grain, where the average            grain diameter of the granular material is greater than 0.2            mm, determined by sieving,    -   wherein the particulate amorphous silicon dioxide produced or        provided preferably comprises particles having a size of less        than 20 μm, more preferably particles having a size of 0.1 μm to        5 μm, most preferably particles having a size of 0.1 μm to 1.5        μm, determined by scanning electron microscopy (SEM) or laser        diffraction.-   4. A process for producing a molding material mixture comprising an    organic binder for use in the foundry industry,    -   comprising the following (and further) steps for production of        the molding material mixture:        -   producing or providing particulate amorphous silicon dioxide            comprising silicon dioxide in a proportion of at least 80%            by weight, preferably in a proportion of at least 90% by            weight, based on the total mass of the particulate amorphous            silicon dioxide,        -   combining the particles of the particulate amorphous silicon            dioxide in an enlargement step to give grains, so as to            result in a granular material comprising a multitude of            individual grains each comprising combined particles and            each comprising a proportion of at least 30% by weight,            preferably at least 40% by weight, more preferably at least            50% by weight, of particulate amorphous silicon dioxide,            based on the mass of the respective grain, where the average            grain diameter of the granular material is greater than 0.2            mm, determined by sieving,    -   wherein the particulate amorphous silicon dioxide produced or        provided preferably comprises particles having a size of less        than 20 μm, more preferably particles having a size of 0.1 μm to        5 μm, most preferably particles having a size of 0.1 μm to 1.5        μm, determined by scanning electron microscopy (SEM) or laser        diffraction.-   5. A process for producing a molding for use in the casting of    metallic cast parts in the foundry industry,    -   comprising the following (and further) steps for production of        the molding:        -   producing or providing particulate amorphous silicon dioxide            comprising silicon dioxide in a proportion of at least 80%            by weight, preferably in a proportion of at least 90% by            weight, based on the total mass of the particulate amorphous            silicon dioxide,        -   combining the particles of the particulate amorphous silicon            dioxide in an enlargement step to give grains, so as to            result in a granular material comprising a multitude of            individual grains each comprising combined particles and            each comprising a proportion of at least 30% by weight,            preferably at least 40% by weight, more preferably at least            50% by weight, of particulate amorphous silicon dioxide,            based on the mass of the respective grain, where the average            grain diameter of the granular material is greater than 0.2            mm, determined by sieving, wherein the particulate amorphous            silicon dioxide produced or provided preferably comprises            particles having a size of less than 20 μm, more preferably            particles having a size of 0.1 μm to 5 μm, most preferably            particles having a size of 0.1 μm to 1.5 μm, determined by            scanning electron microscopy (SEM) or laser diffraction.-   6. The process according to aspect 2 for producing a solid pourable    additive for use as a constituent of an inorganic binder in the    foundry industry,    -   comprising the steps of:        -   producing a granular material by a process according to            aspect 1,        -   comminuting the grains of the granular material, so as to            result in a solid pourable additive.-   7. The process according to aspect 3 for producing an inorganic    binder for use in the foundry industry    -   comprising the steps of:        -   producing a granular material by a process according to            aspect 1,        -   comminuting the grains of the granular material, so as to            result in a solid pourable additive.-   8. The process according to aspect 4 for producing a molding    material mixture comprising an organic binder for use in the foundry    industry,    -   comprising the steps of:        -   producing a granular material by a process according to            aspect 1,        -   comminuting the grains of the granular material, so as to            result in a solid pourable additive.-   9. The process according to aspect 5 for producing a molding for use    in the casting of metallic cast parts in the foundry industry,    -   comprising the steps of:        -   producing a granular material by a process according to            aspect 1,        -   comminuting the grains of the granular material, so as to            result in a solid pourable additive.-   10. The process according to either of the preceding aspects 3 and 7    for producing an inorganic binder for use in the foundry industry,    -   comprising the steps of:        -   producing the solid pourable additive by a process according            to either of aspects 2 and 6,        -   contacting the solid pourable additive produced with            waterglass or suspending the solid pourable additive            produced in waterglass,-   11. The process according to any of the preceding aspects 3, 7 and    10 for producing an inorganic binder for use in the foundry    industry,    -   comprising the steps of:        -   producing a granular material by a process according to any            of aspects 1 to 9,        -   contacting the granular material produced with waterglass,            in the presence or absence of refractory mold base material,            and comminuting the grains of the granular material at the            same time or thereafter.-   12. The process according to either of the preceding aspects 4 and 8    for producing a molding material mixture comprising an inorganic    binder for use in the foundry industry,    -   comprising the steps of:        -   producing the solid pourable additive by a process according            to any of aspects 2, 6 and 10,        -   contacting the solid pourable additive produced with            waterglass or suspending the solid pourable additive            produced in waterglass.-   13. The process according to any of the preceding aspects 4, 8 and    12 for producing a molding material mixture comprising an inorganic    binder for use in the foundry industry,    -   comprising the steps of:        -   producing a granular material by a process according to any            of aspects 1 to 9 or 11,        -   contacting the granular material produced with waterglass,            in the presence or absence of refractory mold base material,            and comminuting the grains of the granular material at the            same time or thereafter.-   14. The process according to either of the preceding aspects 5 and 9    for producing a molding for use in the casting of metallic cast    parts in the foundry industry,    -   comprising the steps of:        -   producing the solid pourable additive by a process according            to any of aspects 2, 6 and 10,        -   contacting the solid pourable additive produced with            waterglass or suspending the solid pourable additive            produced in waterglass.-   15 The process according to any of the preceding aspects 5, 9 and 14    for producing a molding for use in the casting of metallic cast    parts in the foundry industry,    -   comprising the steps of:        -   producing a granular material by a process according to any            of aspects 1 to 9, 11 and 13,        -   contacting the granular material produced with waterglass,            in the presence or absence of refractory mold base material,            and comminuting the grains of the granular material at the            same time or thereafter.-   16. The process according to any of the preceding aspects 4, 8, 12    and 13 for producing a molding material mixture comprising    refractory mold base material and an inorganic binder comprising    waterglass and particulate amorphous silicon dioxide for use in the    foundry industry,    -   comprising the steps of:        -   producing an inorganic binder according to any of aspects 3,            7, 10 and 11,    -   and        -   at the same time mixing the constituents used for production            of the inorganic binder with a refractory mold base            material.-   17. The process according to any of the preceding aspects 4, 8, 12,    13 and 16 for producing a molding material mixture comprising    refractory mold base material and an inorganic binder comprising    waterglass and particulate amorphous silicon dioxide for use in the    foundry industry,    -   comprising the steps of:        -   producing an inorganic binder according to any of aspects 3,            7, 10, 11, 16,    -   and        -   at the same time mixing the constituents used for production            of the inorganic binder with a refractory mold base material    -   and        -   thereafter mixing the inorganic binder produced with a            refractory mold base material.-   18. The process according to any of claims 4, 8, 12, 13, 16 and 17    for producing a molding material mixture comprising refractory mold    base material and an inorganic binder comprising waterglass and    particulate amorphous silicon dioxide for use in the foundry    industry,    -   comprising the steps of:        -   producing an inorganic binder according to any of aspects 3,            7, 10, 11, 16, 17,    -   and        -   thereafter mixing the inorganic binder produced with a            refractory mold base material.-   19. The process according to any of aspects 1 to 5, wherein, in the    step of    -   combining the particles of the particulate amorphous silicon        dioxide in an enlargement step to give grains, so as to result        in a granular material comprising a multitude of individual        grains each comprising combined particles and each comprising a        proportion of at least 30% by weight, preferably at least 40% by        weight, more preferably at least 50% by weight, of particulate        amorphous silicon dioxide, based on the mass of the respective        grain,    -   the average grain diameter of the granular material is greater        than 0.5 mm, preferably greater than 1 mm, determined by        sieving.-   20. The process according to any of the preceding aspects, wherein    the particulate amorphous silicon dioxide comprising silicon dioxide    in a proportion of at least 80% by weight, based on the total mass    of the particulate amorphous silicon dioxide, consists wholly of    particulate synthetic amorphous silicon dioxide.-   21. The process according to any of the preceding aspects, wherein    the particulate amorphous silicon dioxide comprising silicon dioxide    in a proportion of at least 80% by weight, based on the total mass    of the particulate amorphous silicon dioxide, consists partly of    particulate synthetic amorphous silicon dioxide.-   22. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 1 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 30%, based on the proportion of    silicon dioxide in the granular material as a whole.-   23. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 1 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 20%, based on the proportion of    silicon dioxide in the granular material as a whole.-   24. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 1 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 10%, based on the proportion of    silicon dioxide in the granular material as a whole.-   25. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 0.5 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 30%, based on the proportion of    silicon dioxide in the granular material as a whole.-   26. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 0.5 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 20%, based on the proportion of    silicon dioxide in the granular material as a whole.-   27. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 0.5 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 10%, based on the proportion of    silicon dioxide in the granular material as a whole.-   28. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 0.2 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 30%, based on the proportion of    silicon dioxide in the granular material as a whole.-   29. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 0.2 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 20%, based on the proportion of    silicon dioxide in the granular material as a whole.-   30. The process according to any of the preceding aspects, wherein    the proportion of silicon dioxide in the granular material as a    whole, determined by means of x-ray fluorescence analysis, and the    proportion of silicon dioxide in at least 90% of the grains of the    granular material having a grain diameter greater than 0.2 mm,    determined by means of sieving and subsequent x-ray fluorescence    analysis, differs by not more than 10%, based on the proportion of    silicon dioxide in the granular material as a whole.-   31. The process according to any of the preceding aspects, wherein,    in the enlargement step, the particles of the particulate amorphous    silicon dioxide are mixed and/or contacted with one, two or more    further materials independently selected from the group consisting    of:    -   liquids, preferably liquid wetting agents and/or suspension        media, preferably water,    -   particulate materials, preferably particulate inorganic        materials, preferably selected from the group consisting of        oxides of aluminum, preferably aluminum oxide in the alpha        phase, bauxite, oxides of zirconium, preferably zirconium(IV)        oxide, mixed aluminum/silicon oxides, zinc oxide, barium        sulfate, phosphorus compounds, sheet silicates, graphite, carbon        black, glass beads, oxides of magnesium, borosilicates, ceramic        hollow beads, oxidic boron compounds, preferably pulverulent        oxidic boron compounds, and mixtures thereof,    -   water-soluble materials,    -   alkali metal hydroxides,    -   surfactants,    -   film formers,    -   hydrophobizing agents, preferably organosilicon compounds,        silanes, silicones and siloxanes, waxes, paraffins, metal soaps,-    and    -   carbohydrates.-   32. The process according to aspect 31, wherein grains of the    granular material that results from the enlargement step, preferably    at least 90% of the grains of the granular material having a grain    diameter greater than 1 mm, preferably greater than 0.5 mm, more    preferably greater than 0.2 mm, in each case determined by means of    sieving,    -   (i) comprise particulate amorphous silicon dioxide and one, two,        more than two or all of the further solid materials present in        the enlargement step-    and    -   (ii) comprise particulate amorphous silicon dioxide and one, two        or more further materials independently selected from the group        consisting of:        -   particulate materials, preferably particulate inorganic            materials, preferably selected from the group consisting of            oxides of aluminum, preferably aluminum oxide in the alpha            phase, bauxite, oxides of zirconium, preferably            zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc            oxide, barium sulfate, phosphorus compounds, sheet            silicates, graphite, carbon black, glass beads, oxides of            magnesium, borosilicates, ceramic hollow beads, oxidic boron            compounds, preferably pulverulent oxidic boron compounds,            and mixtures thereof,        -   water-soluble materials,        -   alkali metal hydroxides,        -   surfactants,        -   film formers,        -   hydrophobizing agents, preferably organosilicon compounds,            silanes, silicones and siloxanes, waxes, paraffins, metal            soaps,    -   and        -   carbohydrates.-   33. The process according to aspect 31, wherein grains of the    granular material that results from the enlargement step, preferably    at least 90% of the grains of the granular material having a grain    diameter greater than 1 mm, preferably greater than 0.5 mm, more    preferably greater than 0.2 mm, in each case determined by means of    sieving,    -   comprise particulate amorphous silicon dioxide and one, two,        more than two or all of the other solid materials present in the        enlargement step.-   34. The process according to aspect 31, wherein grains of the    granular material that results from the enlargement step, preferably    at least 90% of the grains of the granular material having a grain    diameter greater than 1 mm, preferably greater than 0.5 mm, more    preferably greater than 0.2 mm, in each case determined by means of    sieving,    -   comprise particulate amorphous silicon dioxide and one, two or        more further materials independently selected from the group        consisting of:        -   particulate materials, preferably particulate inorganic            materials, preferably selected from the group consisting of            oxides of aluminum, preferably aluminum oxide in the alpha            phase, bauxite, oxides of zirconium, preferably            zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc            oxide, barium sulfate, phosphorus compounds, sheet            silicates, graphite, carbon black, glass beads, oxides of            magnesium, borosilicates, ceramic hollow beads, oxidic boron            compounds, preferably pulverulent oxidic boron compounds,            and mixtures thereof,        -   water-soluble materials,        -   alkali metal hydroxides,        -   surfactants,        -   film formers,        -   hydrophobizing agents, preferably organosilicon compounds,            silanes, silicones and siloxanes, waxes, paraffins, metal            soaps,    -   and        -   carbohydrates.-   35. The process according to any of the preceding aspects, wherein    -   the producing of particulate amorphous silicon dioxide        comprising silicon dioxide in a proportion of at least 80% by        weight, based on the total mass of the particulate amorphous        silicon dioxide, comprises the step of:        -   mixing two or more different types of particulate amorphous            silicon dioxide, where the two or more types differ by their            particle size distribution and/or their chemical            composition.-   36. The process according to aspect 35, wherein    -   one type of particulate amorphous silicon dioxide has a particle        size distribution having a median in the range from 0.1 to 0.4        μm, determined by laser scattering.-   37. The process according to aspect 35, wherein    -   one type of particulate amorphous silicon dioxide has a particle        size distribution having a median in the range from 0.7 to 1.5        μm, determined by laser scattering.-   38. The process according to aspect 35, wherein    -   one, two, more than two or all of the different types of        particulate amorphous silicon dioxide is selected or are        independently selected from the group consisting of        -   particulate synthetic amorphous silicon dioxide containing            silicon dioxide in a proportion of at least 80% by weight,            based on the total mass of the particulate synthetic            amorphous silicon dioxide, and at least carbon as secondary            constituent, preferably producible by reducing quartz in an            arc furnace;        -   particulate synthetic amorphous silicon dioxide comprising            oxidic zirconium as secondary constituent and preferably            producible by thermal breakdown of ZrSiO₄        -   particulate synthetic amorphous silicon dioxide producible            by oxidizing metallic silicon by means of an oxygenous gas;        -   particulate synthetic amorphous silicon dioxide producible            by quenching a silicon dioxide melt.-   39. The process according to aspect 35,    -   wherein a first type of particulate amorphous silicon dioxide        has a particle size distribution having a median in the range        from 0.1 to 0.4 μm, determined by laser scattering,-    and    -   wherein a further type of particulate amorphous silicon dioxide        has a particle size distribution having a median in the range        from 0.7 to 1.5 μm, determined by laser scattering.-   40. The process according to aspect 35,    -   wherein a first type of particulate amorphous silicon dioxide        has a particle size distribution having a median in the range        from 0.1 to 0.4 μm, determined by laser scattering,-    and    -   wherein one, two, more than two or all the different types of        particulate amorphous silicon dioxide is selected or are        independently selected from the group consisting of        -   particulate synthetic amorphous silicon dioxide containing            silicon dioxide in a proportion of at least 80% by weight,            based on the total mass of the particulate synthetic            amorphous silicon dioxide, and at least carbon as secondary            constituent, preferably producible by reducing quartz in an            arc furnace;        -   particulate synthetic amorphous silicon dioxide comprising            oxidic zirconium as secondary constituent and preferably            producible by thermal breakdown of ZrSiO₄        -   particulate synthetic amorphous silicon dioxide producible            by oxidizing metallic silicon by means of an oxygenous gas;        -   particulate synthetic amorphous silicon dioxide producible            by quenching a silicon dioxide melt.-   41. The process according to aspect 35,    -   wherein a first type of particulate amorphous silicon dioxide        has a particle size distribution having a median in the range        from 0.1 to 0.4 μm, determined by laser scattering,-    and    -   wherein a further type of particulate amorphous silicon dioxide        has a particle size distribution having a median in the range        from 0.7 to 1.5 μm, determined by laser scattering,-    and    -   wherein one, two, more than two or all the different types of        particulate amorphous silicon dioxide is selected or are        independently selected from the group consisting of        -   particulate synthetic amorphous silicon dioxide containing            silicon dioxide in a proportion of at least 80% by weight,            based on the total mass of the particulate synthetic            amorphous silicon dioxide, and at least carbon as secondary            constituent, preferably producible by reducing quartz in an            arc furnace;        -   particulate synthetic amorphous silicon dioxide comprising            oxidic zirconium as secondary constituent and preferably            producible by thermal breakdown of ZrSiO₄        -   particulate synthetic amorphous silicon dioxide producible            by oxidizing metallic silicon by means of an oxygenous gas;        -   particulate synthetic amorphous silicon dioxide producible            by quenching a silicon dioxide melt.-   42. The process according to aspect 35,    -   wherein a further type of particulate amorphous silicon dioxide        has a particle size distribution having a median in the range        from 0.7 to 1.5 μm, determined by laser scattering,-    and    -   wherein one, two, more than two or all the different types of        particulate amorphous silicon dioxide is selected or are        independently selected from the group consisting of        -   particulate synthetic amorphous silicon dioxide containing            silicon dioxide in a proportion of at least 80% by weight,            based on the total mass of the particulate synthetic            amorphous silicon dioxide, and at least carbon as secondary            constituent, preferably producible by reducing quartz in an            arc furnace;        -   particulate synthetic amorphous silicon dioxide comprising            oxidic zirconium as secondary constituent and preferably            producible by thermal breakdown of ZrSiO₄        -   particulate synthetic amorphous silicon dioxide producible            by oxidizing metallic silicon by means of an oxygenous gas;        -   particulate synthetic amorphous silicon dioxide producible            by quenching a silicon dioxide melt.-   43. The process according to any of aspects 35 to 42, wherein at    least 90% of the grains of the granular material having a particle    diameter greater than 0.2 mm, preferably greater than 0.5 mm, more    preferably greater than 1 mm, in each case determined by sieving,    comprise both or at least two of the different types of particulate    amorphous silicon dioxide, preferably determined or confirmed    (especially by sieving according to VDG-Merkblatt P 27, see above),    for example by means of x-ray fluorescence analysis according to DIN    EN ISO 12677, DIN 51001, optionally in combination with optical    and/or spectroscopic methods and/or wet-chemical methods; the person    skilled in the art will choose a suitable method of determination,    preferably with knowledge of the materials used in the process.-   44. The process according to one of the preceding aspects, wherein    the enlargement step comprises one or more measures independently    selected from the group consisting of:    -   granulating    -   extruding-    and    -   agglomerating.-   45. A granular material having an average grain diameter greater    than 0.2 mm, determined by sieving, for production of a pourable    additive for use as a constituent of an inorganic binder in the    foundry industry, comprising particulate amorphous silicon dioxide,    -   (a) wherein the granular material additionally comprises        -   one, two or more further materials independently selected            from the group consisting of:            -   particulate materials, preferably particulate inorganic                materials, preferably selected from the group consisting                of oxides of aluminum, preferably aluminum oxide in the                alpha phase, bauxite, oxides of zirconium, preferably                zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc                oxide, barium sulfate, phosphorus compounds, sheet                silicates, graphite, carbon black, glass beads, oxides                of magnesium, borosilicates, ceramic hollow beads,                oxidic boron compounds, preferably pulverulent oxidic                boron compounds, and mixtures thereof,            -   water-soluble materials,            -   alkali metal hydroxides,            -   surfactants,            -   film formers,            -   hydrophobizing agents, preferably organosilicon                compounds, silanes, silicones and siloxanes, waxes,                paraffins, metal soaps,        -   and            -   carbohydrates,        -   wherein at least 90% of the grains of the granular material            having a grain diameter greater than 0.2 mm, preferably            greater than 0.5 mm, more preferably greater than 1 mm, in            each case determined by sieving, comprise particulate            amorphous silicon dioxide, and one, two or more of said            further materials,    -   and/or    -   (b) wherein the particulate amorphous silicon dioxide comprises        a proportion of at least 80% by weight of silicon dioxide, based        on the total mass of the particulate amorphous silicon dioxide,        preferably consisting wholly or partly of particulate synthetic        amorphous silicon dioxide,    -   and/or    -   (c) wherein the proportion of silicon dioxide in the granular        material as a whole, determined by means of x-ray fluorescence        analysis, and the proportion of silicon dioxide in at least 90%        of the grains of the granular material having a grain diameter        greater than 1 mm, in each case determined by means of sieving        and subsequent x-ray fluorescence analysis, differs by not more        than 30%, preferably differs by not more than 20%, more        preferably differs by not more than 10%, based on the proportion        of silicon dioxide in the granular material as a whole,    -   and/or    -   (d) wherein, in the granular material, the particulate amorphous        silicon dioxide comprises two or more different types of        particulate amorphous silicon dioxide, where the two or more        types differ by their chemical composition,        -   wherein preferably one, two, more than two or all of the            different types of particulate amorphous silicon dioxide is            selected or are independently selected from the group            consisting of:            -   particulate synthetic amorphous silicon dioxide                containing silicon dioxide in a proportion of at least                80% by weight, based on the total mass of the                particulate synthetic amorphous silicon dioxide, and at                least carbon as secondary constituent, preferably                producible by reducing quartz in an arc furnace;            -   particulate synthetic amorphous silicon dioxide                comprising oxidic zirconium as secondary constituent and                preferably producible by thermal breakdown of ZrSiO₄            -   particulate synthetic amorphous silicon dioxide                producible by oxidizing metallic silicon by means of an                oxygenous gas;            -   particulate synthetic amorphous silicon dioxide                producible by quenching a silicon dioxide melt    -   and/or    -   (e) wherein the granular material is producible by a process        according to any of aspects 1 to 9 or any of aspects 20 to 44.-   46. A granular material having an average grain diameter greater    than 0.2 mm, determined by sieving, for production of a pourable    additive for use as a constituent of an inorganic binder in the    foundry industry, comprising particulate amorphous silicon dioxide,    -   (a) wherein the granular material additionally comprises        -   one, two or more further materials independently selected            from the group consisting of            -   particulate materials, preferably particulate inorganic                materials, preferably selected from the group consisting                of oxides of aluminum, preferably aluminum oxide in the                alpha phase, bauxite, oxides of zirconium, preferably                zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc                oxide, barium sulfate, phosphorus compounds, sheet                silicates, graphite, carbon black, glass beads, oxides                of magnesium, borosilicates, ceramic hollow beads,                oxidic boron compounds, preferably pulverulent oxidic                boron compounds, and mixtures thereof,            -   water-soluble materials,            -   alkali metal hydroxides,            -   surfactants,            -   film formers,            -   hydrophobizing agents, preferably organosilicon                compounds, silanes, silicones and siloxanes, waxes,                paraffins, metal soaps,        -   and            -   carbohydrates,        -   wherein at least 90% of the grains of the granular material            having a grain diameter greater than 0.2 mm, preferably            greater than 0.5 mm, more preferably greater than 1 mm, in            each case determined by sieving, comprise particulate            amorphous silicon dioxide, and one, two or more of said            further materials,    -   and    -   (b) wherein the particulate amorphous silicon dioxide comprises        a proportion of at least 80% by weight of silicon dioxide, based        on the total mass of the particulate amorphous silicon dioxide,        preferably consisting wholly or partly of particulate synthetic        amorphous silicon dioxide,    -   and    -   (c) wherein the proportion of silicon dioxide in the granular        material as a whole, determined by means of x-ray fluorescence        analysis, and the proportion of silicon dioxide in at least 90%        of the grains of the granular material having a grain diameter        greater than 1 mm, in each case determined by means of sieving        and subsequent x-ray fluorescence analysis, differs by not more        than 30%, preferably differs by not more than 20%, more        preferably differs by not more than 10%, based on the proportion        of silicon dioxide in the granular material as a whole,    -   and    -   (d) wherein, in the granular material, the particulate amorphous        silicon dioxide comprises two or more different types of        particulate amorphous silicon dioxide, where the two or more        types differ by their chemical composition,        -   wherein preferably one, two, more than two or all of the            different types of particulate amorphous silicon dioxide is            selected or are independently selected from the group            consisting of            -   particulate synthetic amorphous silicon dioxide                containing silicon dioxide in a proportion of at least                80% by weight, based on the total mass of the                particulate synthetic amorphous silicon dioxide, and at                least carbon as secondary constituent, preferably                producible by reducing quartz in an arc furnace;            -   particulate synthetic amorphous silicon dioxide                comprising oxidic zirconium as secondary constituent and                preferably producible by thermal breakdown of ZrSiO₄            -   particulate synthetic amorphous silicon dioxide                producible by oxidizing metallic silicon by means of an                oxygenous gas;            -   particulate synthetic amorphous silicon dioxide                producible by quenching a silicon dioxide melt    -   and    -   (e) wherein the granular material is producible by a process        according to any of aspects 1 to 9 or any of aspects 20 to 44.-   47. A granular material having an average grain diameter greater    than 0.2 mm, determined by sieving, for production of a pourable    additive for use as a constituent of an inorganic binder in the    foundry industry, comprising particulate amorphous silicon dioxide,    -   wherein the granular material additionally comprises        -   one, two or more further materials independently selected            from the group consisting of:            -   particulate materials, preferably particulate inorganic                materials, preferably selected from the group consisting                of oxides of aluminum, preferably aluminum oxide in the                alpha phase, bauxite, oxides of zirconium, preferably                zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc                oxide, barium sulfate, phosphorus compounds, sheet                silicates, graphite, carbon black, glass beads, oxides                of magnesium, borosilicates, ceramic hollow beads,                oxidic boron compounds, preferably pulverulent oxidic                boron compounds, and mixtures thereof,            -   water-soluble materials,            -   alkali metal hydroxides,            -   surfactants,            -   film formers,            -   hydrophobizing agents, preferably organosilicon                compounds, silanes, silicones and siloxanes, waxes,                paraffins, metal soaps,        -   and            -   carbohydrates,        -   wherein at least 90% of the grains of the granular material            having a grain diameter greater than 0.2 mm, preferably            greater than 0.5 mm, more preferably greater than 1 mm, in            each case determined by sieving, comprise particulate            amorphous silicon dioxide, and one, two or more of said            further materials.-   48. A granular material having an average grain diameter greater    than 0.2 mm, determined by sieving, for production of a pourable    additive for use as a constituent of an inorganic binder in the    foundry industry, comprising particulate amorphous silicon dioxide,    -   wherein the particulate amorphous silicon dioxide comprises a        proportion of at least 80% by weight of silicon dioxide, based        on the total mass of the particulate amorphous silicon dioxide,        preferably consisting wholly or partly of particulate synthetic        amorphous silicon dioxide,-   49 A granular material having an average grain diameter greater than    0.2 mm, determined by sieving, for production of a pourable additive    for use as a constituent of an inorganic binder in the foundry    industry, comprising particulate amorphous silicon dioxide,    -   wherein the proportion of silicon dioxide in the granular        material as a whole, determined by means of x-ray fluorescence        analysis, and the proportion of silicon dioxide in at least 90%        of the grains of the granular material having a grain diameter        greater than 1 mm, in each case determined by means of sieving        and subsequent x-ray fluorescence analysis, differs by not more        than 30%, preferably differs by not more than 20%, more        preferably differs by not more than 10%, based on the proportion        of silicon dioxide in the granular material as a whole.-   50. A granular material having an average grain diameter greater    than 0.2 mm, determined by sieving, for production of a pourable    additive for use as a constituent of an inorganic binder in the    foundry industry, comprising particulate amorphous silicon dioxide,    -   wherein, in the granular material, the particulate amorphous        silicon dioxide comprises two or more different types of        particulate amorphous silicon dioxide, where the two or more        types differ by their chemical composition,    -   wherein preferably one, two, more than two or all of the        different types of particulate amorphous silicon dioxide is        selected or are independently selected from the group consisting        of        -   particulate synthetic amorphous silicon dioxide containing            silicon dioxide in a proportion of at least 80% by weight,            based on the total mass of the particulate synthetic            amorphous silicon dioxide, and at least carbon as secondary            constituent, preferably producible by reducing quartz in an            arc furnace;        -   particulate synthetic amorphous silicon dioxide comprising            oxidic zirconium as secondary constituent and preferably            producible by thermal breakdown of ZrSiO₄        -   particulate synthetic amorphous silicon dioxide producible            by oxidizing metallic silicon by means of an oxygenous gas;        -   particulate synthetic amorphous silicon dioxide producible            by quenching a silicon dioxide melt.-   51. A granular material having an average grain diameter greater    than 0.2 mm, determined by sieving, for production of a pourable    additive for use as a constituent of an inorganic binder in the    foundry industry, comprising particulate amorphous silicon dioxide,    -   wherein the granular material is producible by a process        according to any of aspects 1 to 9 or any of aspects 20 to 44.-   52. A kit comprising, as a component in a spatially separate    arrangement, a granular material according to any of aspects 45 to    51, preferably    -   kit for production of an inorganic binder, preferably a binder        comprising and/or consisting of an inorganic multicomponent        binder system, at least comprising, as components in a mutually        spatially separate arrangement,        -   a granular material according to any of aspects 45 to 51    -   and        -   a solution or dispersion comprising waterglass.-   53. An apparatus for performing a process according to any of    aspects 1 to 44, comprising    -   a reservoir vessel containing particulate amorphous silicon        dioxide, comprising silicon dioxide in a proportion of at least        80% by weight, based on the total mass of the particulate        amorphous silicon dioxide,    -   a mixing or contacting device for mixing or contacting the        particulate amorphous silicon dioxide with one, two or more        further materials,    -   a device for granulating, extruding and/or agglomerating the        particulate amorphous silicon dioxide that has been mixed or        contacted with one, two or more further materials.-   54. The apparatus according to aspect 53, additionally comprising    one or more apparatus elements selected from the group consisting of    -   device for transferring particulate amorphous silicon dioxide        from the reservoir vessel into the mixing or contacting        apparatus,    -   one or more reservoir vessels containing liquid, preferably        liquid wetting agent and/or suspension medium, preferably water,    -   one or more reservoir vessels containing particulate material,        preferably particulate inorganic material, preferably selected        from the group consisting of oxides of aluminum, preferably        aluminum oxide in the alpha phase, bauxite, oxides of zirconium,        preferably zirconium(IV) oxide, mixed aluminum/silicon oxides,        zinc oxide, barium sulfate, phosphorus compounds, sheet        silicates, graphite, carbon black, glass beads, oxides of        magnesium, borosilicates, ceramic hollow beads, oxidic boron        compounds, preferably pulverulent oxidic boron compounds, and        mixtures thereof,    -   one or more reservoir vessels containing a water-soluble        material,    -   one or more reservoir vessels containing one or more        surfactants,        -   one or more reservoir vessels containing one or more            hydrophobizing agents,        -   one or more reservoir vessels containing one or more            carbohydrates.-   55. The apparatus according to aspect 53 or 54, additionally    comprising a device for dispensing or transporting granular material    produced.-   56. The use of particulate amorphous silicon dioxide for production    of or as a constituent of a granular material according to aspect 45    to 51.-   57. The use of a granular material according to any of aspects 45 to    51 for production of a solid pourable additive with homogenized    grain composition for use as a constituent of an inorganic binder in    the foundry industry.

The invention is elucidated in detail hereinafter with reference tofigures.

FIG. 1 shows a flow diagram of a first embodiment of an inventiveprocess 100 for producing a molding material mixture 107 for use in thefoundry industry.

In a first step 101 of the process 100, a particulate amorphous silicondioxide is produced or provided, as defined above.

In a second (enlargement) step 102, the particles of the particulateamorphous silicon dioxide are combined to give grains, so as to resultin an above-defined granular material 103 comprising a multitude ofindividual grains.

The granular material produced is already a product of a process of theinvention.

In a further step 104, the granular material produced is contacteddirectly with waterglass, so as to result in an inorganic binder 105.The inorganic binder produced is likewise a product of a process of theinvention.

In an additional step 106, the inorganic binder 105 produced is mixedwith a refractory mold base material, so as to result in a moldingmaterial mixture 107 as product of the process of the invention.

In a further step 108, the molding material mixture 107 produced ismolded and (at least partly) cured, so as to result in a molding 109 asproduct of the process of the invention.

FIG. 2 shows a flow diagram of a second embodiment of an inventiveprocess 200 for producing a molding material mixture 209 for use in thefoundry industry.

In a first step 201 of the process 200, a particulate amorphous silicondioxide is produced or provided, as defined above.

In a second (enlargement) step 202, the particles of the particulateamorphous silicon dioxide are combined to give grains, so as to resultin an above-defined granular material 203 comprising a multitude ofindividual grains. The granular material produced is already a productof a process of the invention.

In a next step 204, the grains of the granular material 203 arecomminuted, so as to form a solid pourable additive 205. The additiveproduced is likewise a product of a process of the invention.

In a further step 206, the granular material produced is contacted withwaterglass, so as to result in an inorganic binder 207. The inorganicbinder produced is likewise a product of a process of the invention.

In an additional step 208, the inorganic binder 207 produced is mixedwith a refractory mold base material, so as to result in a moldingmaterial mixture 209 as product of the process of the invention.

In a further step 210, the molding material mixture 209 produced ismolded and (at least partly) cured, so as to result in a molding 211 asproduct of the process of the invention.

FIG. 3 shows a flow diagram of an alternative embodiment of an inventiveprocess 300 for producing a molding material mixture 309 for use in thefoundry industry.

In a first step 301 of the process 300, a particulate amorphous silicondioxide is produced or provided, as defined above.

In a separate step 301 a, further materials are produced or provided (asdefined in aspect 27 and the description above).

In a next (enlargement) step 302, the particles of the particulateamorphous silicon dioxide are combined to grains, wherein the furthermaterials produced or provided in step 301 a are added before or duringstep 302 a, such that the particles of the particulate amorphous silicondioxide are mixed and/or contacted with these further materials in theenlargement step, such that the enlargement step results in anabove-defined granular material 303 comprising a multitude of individualgrains. These individual grains comprise the particulate amorphoussilicon dioxide and the further materials. The granular materialproduced is already a product of a process of the invention.

In a subsequent step 304, the grains of the granular material 303 arecomminuted, so as to form a solid pourable additive 305. The additiveproduced is likewise a product of a process of the invention.

In a further step 306, the granular material produced is contacted withwaterglass, so as to result in an organic binder 307. The inorganicbinder produced is likewise a product of a process of the invention.

In a next step 308, the inorganic binder 307 produced is mixed with arefractory mold base material, so as to result in a molding materialmixture 309 as product of the process of the invention.

In a further step 310, the molding material mixture 309 produced ismolded and (at least partly) cured, so as to result in a molding 311 asproduct of the process of the invention.

Steps 102, 202 and 302 shown in FIGS. 1, 2 and 3 represent stepsessential to the respective embodiment of the process of the invention.There is no model for such steps in the prior art.

EXAMPLE 1—METHODOLOGY OF DETERMINATION OF PARTICLE SIZE DISTRIBUTION BYMEANS OF LASER SCATTERING

The selection of the substances in this example is merely illustrative,and it is also possible to determine particle size distributions ormedians of other particulate species to be used in the context of thepresent invention by means of laser scattering according to theprocedure in this example.

1.1 Sample Preparation:

By way of example, particle size distributions of silica fume particles(CAS number: 65012-64-2; particulate amorphous silicon dioxide) that arecommercially available (RW Silicium GmbH) and in particulate powder formfrom Si production were determined.

In each case, about 1 teaspoon of this particulate amorphous silicondioxide was admixed with about 100 mL of demineralized water, and theresultant mixture was stirred with a magnetic stirrer (IKAMAG RET) at astirrer speed of 500 revolutions per minute for 30 seconds.Subsequently, an ultrasound probe (from Hielscher; model: UP200HT)preadjusted to 100% amplitude, equipped with a S26d7 sonotrode (fromHielscher), was immersed into the sample, and the sample was sonicatedtherewith. The sonication was continuous (not pulsed). For the silicafume particles examined, optimal sonication times of 300 seconds werechosen, which were determined beforehand as described in point 1.3 belowof example 1.

1.2 Laser Scattering Measurements:

The measurements were conducted with a Horiba LA-960 instrument (LA-960hereinafter). For the measurements, circulation speed was set to 6,stirrer speed to 8, data recording for the sample to 30 000, convergencefactor to 15, the mode of distribution to volume, and refractive index(R) to 1.50-0.01i (1.33 for demineralized water dispersion medium) andrefractive index (B) to 1.50-0.01i (1.33 for demineralized waterdispersion medium). Laser scattering measurements were conducted at roomtemperature (20° C. to 25° C.).

The measurement chamber of the LA-960 was filled to an extent of threequarters with demineralized water (maximum fill level). Then the stirrerwas started at the set speed, the circulation was switched on and thewater was degassed. Subsequently, a zero measurement was conducted withthe parameters specified.

A disposable pipette was then used to take a 0.5-3.0 mL sample centrallyfrom the sample prepared according to point 1.1 of example 1 immediatelyafter the ultrasound treatment. Subsequently, the complete contents ofthe pipette were introduced into the measurement chamber, such that thetransmittance of the red laser was between 80% and 90% and thetransmittance of the blue laser was between 70% and 90%. Then themeasurement was started. The measurements were evaluated in an automatedmanner on the basis of the parameters specified.

For the silica fume particles examined from Si production, a particlesize distribution was ascertained with a median rounded to the secondpost-decimal place.

1.3 Determination of Optimal Sonication Time:

The optimal duration of ultrasound sonication, which is dependent on thetype of sample, is ascertained by conducting a measurement series withdifferent sonication times for each particulate species. This is done byextending the sonication time, starting from 10 seconds, by 10 secondseach time for every further sample, and determining the respectiveparticle size distribution by means of laser scattering (LA-960)immediately after the end of sonication as described in point 1.2 ofexample 1. With increasing duration of sonication, the medianascertained in the particle size distribution falls at first, beforeultimately rising again at longer sonication times. For the ultrasoundsonications described in point 1.1 of example 1, the sonication timechosen was that at which, in these measurements series, the lowestmedian of the particle size distribution was determined for the particlespecies; this sonication time is the “optimal” sonication time.

EXAMPLE 2—PRODUCTION METHOD FOR GRANULAR MATERIALS

10 kg of synthetic particulate amorphous silicon dioxide (in powderform, particle size <1.5 μm; e.g. Microsilica POS B-W 90 LD (PossehlErzkontor GmbH) or silica fume (Doral Fused Materials Pty., Ltd.);production process in each case: production of ZrO₂ and SiO₂ fromZrSiO₄) are introduced into a plowshare mixer (from Gebrüder LödigeMaschinenbau GmbH, model L50), and the plowshare mixer, for mixing, isoperated at a speed of rotation of the plowshare shaft of 180revolutions per minute and of the bladed head of 3000 revolutions perminute. During the mixing, water is fed into the synthetic particulateamorphous silicon dioxide in several steps: 0.25 kg of water followed bya mixing time of 60 seconds, then an additional 0.5 kg of water followedby a mixing time of a further 240 seconds, then an additional 0.5 kg ofwater followed by a mixing time of a further 120 seconds, and then anadditional 1.0 kg of water followed by a mixing time after a furthermixing time of 180 seconds.

The suspension thus produced is dripped by means of a pipette inindividual droplets onto a commercial aluminum foil (which hasoptionally been sprayed with separating agent) heated to 250° C. on ahotplate and dried, such that the particles of the powder used combineto form grains and result in a granular material of the invention. Thehotplate is preferably protected here from soiling with a further layerof aluminum foil (arranged beneath the layer that comes into contactwith the suspension).

The proportion by mass of the particles having a size of less than 20μm, determined by means of laser scattering, in the granular material islower than in the particulate amorphous silicon dioxide.

EXAMPLE 3—BULK DENSITY; REDUCED EVOLUTION OF DUST

Bulk density is determined with a laboratory balance (measurementuncertainty ±0.1 g), a metal measuring cylinder having a volume of(100±0.5) mL and an internal diameter of (45±5) mm, and a funnel(according to DIN EN ISO 60) with a closed lower opening.

The funnel is secured centrally above the measuring cylinder at a heightof 20 mm to 30 mm, and the sample is mixed well. About 120 mL to 130 mLof the sample is introduced into the funnel. The closure of the funnelis opened quickly, such that the sample material drops into thecylinder. Excess sample material is stripped off the cylinder with theaid of a straight-edged article, and then the contents of the cylinderare weighed; the mass of the contents of the cylinder is m_(sample).

The evaluation is made by the following formula:

${{Bulk}\mspace{14mu}{{density}\mspace{14mu}\left\lbrack \frac{g}{L} \right\rbrack}} = {{m_{sample}\lbrack g\rbrack} \cdot {10\left\lbrack \frac{1}{L} \right\rbrack}}$

The result is reported to 1 g/L.

According to example 2, synthetic particulate amorphous silicon dioxidehaving a bulk density of 550 g/L was used to produce a granularmaterial. After drying, the granular material of the invention thusobtained had an average grain diameter of 6 mm and a bulk density of 950g/L.

When poured, the granular material showed much lower evolution of (fine)dust than the starting material, the synthetic particulate amorphoussilicon dioxide having a bulk density of 550 g/L.

EXAMPLE 4—EXAMINATION OF ONE-HOUR STRENGTH OF DIFFERENT TEST BARS

4.1 Production of a Molding Material Mixture 4-A

0.80 part by weight of synthetic particulate amorphous silicon dioxidehaving a bulk density of about 550 g/L (pulverulent; non-granulated;e.g. Microsilica POS B-W 90 LD (Possehl Erzkontor GmbH) or silica fume(Doral Fused Materials Pty., Ltd.); production process in each case:production of ZrO₂ and SiO₂ from ZrSiO₄) was mixed manually with 100parts by weight of H-S 00232 sand (quartz sand, from Quarzwerke GmbH,AFS grain fineness number 47). Then 2.00 parts by weight of a waterglass-based liquid binder (commercial material named Cordis 9032;Hüttenes-Albertus Chemische Werke GmbH) was added and all componentswere mixed with one another for 120 s in a bull mixer (RN 10/20 type,from Morek Multiserw) at 220 revolutions per minute, such that thematerials used were distributed homogeneously, and so as to result in amolding material mixture.

4.2 Production of a Molding Material Mixture 4-B

Synthetic particulate amorphous silicon dioxide having a bulk density of550 g/L (identical to the material used in example 4.1) and water wereused according to example 2 to produce a granular material. The granularmaterial thus produced was ground in a mixer (from Bosch, Universal PlusMUM 6N11 food processor) for 10 s so as to result in a solid pourableadditive.

0.80 part by weight of this solid pourable additive was mixed manuallywith 100 parts by weight of H-S 00232 sand (quartz sand, from QuarzwerkeGmbH, AFS grain fineness number 47). Then 2.00 parts by weight of awater glass-based liquid binder (commercial material named Cordis 9032;Hüttenes-Albertus Chemische Werke GmbH) was added and all componentswere mixed with one another for 120 s in a bull mixer (RN 10/20 type,from Morek Multiserw) at 220 revolutions per minute, such that thematerials used were distributed homogeneously, and so as to result in amolding material mixture.

4.3 Production of a Molding Material Mixture 4-C

From 20.05 kg of synthetic particulate amorphous silicon dioxide havinga bulk density of about 550 g/L (identical to the material used inexample 4.1) was introduced into a plowshare mixer (from Gebrüder LödigeMaschinenbau GmbH, model L50). 3 kg of water was fed into the syntheticparticulate amorphous silicon dioxide, and the plowshare mixer wasoperated at a speed of rotation of the plowshare shaft of 180revolutions per minute and of the bladed head of 3000 revolutions perminute for 120 seconds. Then the bladed head was switched off and mixingwas continued at a speed of rotation of the plowshare shaft of 180revolutions per minute, such that a soft granular material was formed.

A portion of the still-moist soft granular material was then dried toconstant weight at 105° C., so as to result in a (dried) granularmaterial. The cooled dried material was then classified by means of asieving tower in accordance with VDG-Merkblatt P 27, October 1999, andthe fractions <125 μm were discarded. The sieving yield was about 85%.

When poured, the classified granular material showed much lowerevolution of (fine) dust than the starting material, the particulateamorphous silicon dioxide having a bulk density of about 550 g/L.

The classified granular material thus produced was ground in a mixer(from Bosch, Universal Plus MUM 6N11 food processor) for 10 s so as toform a solid pourable additive.

0.80 part by weight of this solid pourable additive was mixed manuallywith 100 parts by weight of H-S 00232 sand (quartz sand, from QuarzwerkeGmbH, AFS grain fineness number 47). Then 2.00 parts by weight of awater glass-based liquid binder (commercial material named Cordis 9032;Hüttenes-Albertus Chemische Werke GmbH) was added and all componentswere mixed with one another for 120 s in a bull mixer (RN 10/20 type,from Morek Multiserw) at 220 revolutions per minute, such that thematerials used were distributed homogeneously, and so as to result in amolding material mixture.

4.4 Production of Test Bars

Molding material mixtures 4-A, 4-B and 4-C produced according to points4.1, 4.2 and 4.3 of example 4 were each formed to test bars havingdimensions of 22.4 mm×22.4 mm×185 mm. For this purpose, the respectivemolding material mixtures were introduced with compressed air (4 bar)and a shooting time of 3 seconds into a mold for test bars having atemperature of 160° C. Subsequently, the test bars were subjected to hotcuring at 160° C. without gas supply for 30 seconds. Thereafter, themold was opened, and the cured test bars were removed and stored forcooling.

4.5 Determination of One-Hour Strength

The test bars produced from molding material mixtures 4-A, 4-B and 4-Caccording to point 4.4 of example 4, after a cooling time of one hour,were introduced into a Georg Fischer strength tester, equipped with a3-point bending device (from Morek Multiserw), and the force that led tofracture of the test bar was measured. The value read off (in N/cm²)indicated the one-hour strength. Results are shown in table 1, with therespective one-hour strength figure corresponding to a median from 6individual measurements.

TABLE 1 Molding material One-hour strength mixture no. (N/cm²) 4-A 5004-B 520 4-C 520

The results listed in table 1 show that test bars produced using agranular material (produced by a process of the invention) or a solidpourable additive (produced by a process of the invention) surprisinglyhave elevated one-hour strength.

EXAMPLE 5—PRODUCTION OF GRANULAR MATERIALS WITH HOMOGENEOUS DISTRIBUTIONOF MULTIPLE ADDITIVES

Analogously to the production method from example 2, granular materialswere produced in a multitude of in-house experiments, with addition ofone or more of the following substances as a further material, in eachcase in addition to the particulate amorphous silicon dioxide used:

-   -   liquids, preferably liquid suspension media, preferably water,    -   particulate materials, preferably particulate inorganic        materials, preferably selected from the group consisting of        oxides of aluminum, preferably aluminum oxide in the alpha        phase, bauxite, oxides of zirconium, preferably zirconium(IV)        oxide, mixed aluminum/silicon oxides, zinc oxide, barium        sulfate, phosphorus compounds, sheet silicates, graphite, carbon        black, glass beads, oxides of magnesium, borosilicates, ceramic        hollow beads, oxidic boron compounds, preferably pulverulent        oxidic boron compounds, and mixtures thereof,    -   water-soluble materials,    -   alkali metal hydroxides,    -   surfactants, preferably selected from the group consisting of:        -   oleyl sulfate, stearyl sulfate, palmityl sulfate, myristyl            sulfate, lauryl sulfate, decyl sulfate, octyl sulfate,            2-ethylhexyl sulfate, 2-ethyloctyl sulfate, 2-ethyldecyl            sulfate, palmitoleyl sulfate, linolyl sulfate, lauryl            sulfonate, 2-ethyldecyl sulfonate, palmityl sulfonate,            stearyl sulfonate, 2-ethylstearyl sulfonate, linolyl            sulfonate, hexyl phosphate, 2-ethylhexyl phosphate, capryl            phosphate, lauryl phosphate, myristyl phosphate, palmityl            phosphate, palmitoleyl phosphate, oleyl phosphate, stearyl            phosphate, poly(ethane-1,2-diyl)phenol hydroxyphosphate,            poly(ethane-1,2-diyl)stearyl phosphate,            poly(ethane-1,2-diyl)oleyl phosphate, polycarboxylate ethers            in water (Melpers 0030, from BASF), modified polyacrylate in            water (Melpers VP 4547/240 L, from BASF), 2-ethylhexyl            sulfate in water (Texapon EHS, from Cognis), polyglucoside            in water (Glukopon 225 DK, from Cognis), sodium octylsulfate            in water (Texapon 842, from Lakeland), modified carboxylate            ethers (Castament ES 60, solid-state, from BASF).    -   film formers, preferably polyvinylalcohol and/or acrylic acid,    -   rheological additives (thickeners, suspension aids), preferably        selected from the group consisting of:        -   swellable clays, preferably sodium bentonite or            attapulgite/palygorskite,        -   swellable polymers, preferably cellulose derivatives,            especially carboxymethyl, methyl, ethyl, hydroxyethyl and            hydroxypropyl cellulose, plant mucilages,            polyvinylpyrrolidone, pectin, gelatin, agar-agar,            polypeptides and/or alginates,    -   hydrophobizing agents, preferably organosilicon compounds,        silanes, silanols, preferably trimethylsilanol, silicones and        siloxanes, preferably polydimethylsiloxane, waxes, paraffins,        metal soaps,    -    and    -   carbohydrates.

Granular materials were obtained in an analogous manner in each case.The granular materials obtained can each be processed by grinding togive solid pourable additive. Granular materials or solid pourableadditives were each processed successfully to give molding materialmixtures, and these were processed further to give test bars.

We claim:
 1. A process for producing an article for use in the foundryindustry selected from the group consisting of granular material forproduction of a pourable additive for use as a constituent of aninorganic binder in the foundry industry, solid pourable additive foruse as a constituent of an inorganic binder in the foundry industry,inorganic binder for use in the foundry industry, molding materialmixture comprising an inorganic binder for use in the foundry industry,and moldings for use in the casting of metallic cast parts in thefoundry industry, comprising the following steps for production of thearticle: producing or providing particulate amorphous silicon dioxidecomprising silicon dioxide in a proportion of at least 80% by weight,based on the total mass of the particulate amorphous silicon dioxide,combining the particles of the particulate amorphous silicon dioxide inan enlargement step to give grains, so as to result in a granularmaterial comprising a multitude of individual grains each comprisingcombined particles and each comprising a proportion of at least 30% byweight of particulate amorphous silicon dioxide, based on the mass ofthe respective grain, where the average grain diameter of the granularmaterial is greater than 0.2 mm, determined by sieving.
 2. The processas claimed in claim 1 for producing an article for use in the foundryindustry selected from the group consisting of solid pourable additivefor use as a constituent of an inorganic binder in the foundry industry,inorganic binder for use in the foundry industry, molding materialmixture comprising an inorganic binder for use in the foundry industry,and moldings for use in the casting of metallic cast parts in thefoundry industry, comprising the steps of: producing a granular materialby a process as claimed in claim 1, comminuting the grains of thegranular material, so as to result in a solid pourable additive.
 3. Theprocess as claimed in claim 1 for producing an article for use in thefoundry industry selected from the group consisting of inorganic binderfor use in the foundry industry, molding material mixture comprising aninorganic binder for use in the foundry industry, and moldings for usein the casting of metallic cast parts in the foundry industry, (i)comprising the steps of: producing the solid pourable additive by aprocess as claimed in claim 1, contacting the solid pourable additiveproduced with waterglass or suspending the solid pourable additiveproduced in waterglass, or (ii) comprising the steps of: producing agranular material by a process as claimed in claim 1, contacting thegranular material produced with waterglass, in the presence or absenceof refractory mold base material, and comminuting the grains of thegranular material at the same time or thereafter.
 4. The process asclaimed in claim 1 for producing a molding material mixture comprisingrefractory mold base material and an inorganic binder comprisingwaterglass and particulate amorphous silicon dioxide for use in thefoundry industry, comprising the steps of: producing an inorganic binderas per claim 1, and (i) at the same time mixing the constituents usedfor production of the inorganic binder with a refractory mold basematerial and/or (ii) thereafter mixing the inorganic binder producedwith a refractory mold base material.
 5. The process as claimed in claim1, wherein, in the step of combining the particles of the particulateamorphous silicon dioxide in an enlargement step to give grains, so asto result in a granular material comprising a multitude of individualgrains each comprising combined particles and each comprising aproportion of at least 30% by weight, preferably at least 40% by weight,more preferably at least 50% by weight, of particulate amorphous silicondioxide, based on the mass of the respective grain, the average graindiameter of the granular material is greater than 0.5 mm, preferablygreater than 1 mm, determined by sieving.
 6. The process as claimed inclaim 1, wherein the particulate amorphous silicon dioxide comprisingsilicon dioxide in a proportion of at least 80% by weight, based on thetotal mass of the particulate amorphous silicon dioxide, consists whollyor partly of particulate synthetic amorphous silicon dioxide.
 7. Theprocess as claimed in claim 1, wherein the proportion of silicon dioxidein the granular material as a whole, determined by means of x-rayfluorescence analysis, and the proportion of silicon dioxide in at least90% of the grains of the granular material having a grain diametergreater than 1 mm, preferably greater than 0.5 mm, more preferablygreater than 0.2 mm, in each case determined by means of sieving andsubsequent x-ray fluorescence analysis, differs by not more than 30%,preferably differs by not more than 20%, more preferably differs by notmore than 10%, based on the proportion of silicon dioxide in thegranular material as a whole.
 8. The process as claimed in claim 1,wherein, in the enlargement step, the particles of the particulateamorphous silicon dioxide are mixed and/or contacted with one, two ormore further materials independently selected from the group consistingof: liquids, preferably liquid wetting agents and/or suspension media,preferably water, particulate materials, preferably particulateinorganic materials, preferably selected from the group consisting ofoxides of aluminum, preferably aluminum oxide in the alpha phase,bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixedaluminum/silicon oxides, zinc oxide, barium sulfate, phosphoruscompounds, sheet silicates, graphite, carbon black, glass beads, oxidesof magnesium, borosilicates, ceramic hollow beads, oxidic boroncompounds, preferably pulverulent oxidic boron compounds, and mixturesthereof, water-soluble materials, alkali metal hydroxides, surfactants,film formers, hydrophobizing agents, preferably organosilicon compounds,silanes, silicones and siloxanes, waxes, paraffins, metal soaps,  andcarbohydrates.
 9. The process as claimed in claim 8, wherein grains ofthe granular material that results from the enlargement step, preferablyat least 90% of the grains of the granular material having a graindiameter greater than 1 mm, preferably greater than 0.5 mm, morepreferably greater than 0.2 mm, in each case determined by means ofsieving, (i) comprise particulate amorphous silicon dioxide and one,two, more than two or all of the further solid materials present in theenlargement step and/or (ii) comprise particulate amorphous silicondioxide and one, two or more further materials independently selectedfrom the group consisting of: particulate materials, preferablyparticulate inorganic materials, preferably selected from the groupconsisting of oxides of aluminum, preferably aluminum oxide in the alphaphase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide,mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphoruscompounds, sheet silicates, graphite, carbon black, glass beads, oxidesof magnesium, borosilicates, ceramic hollow beads, oxidic boroncompounds, preferably pulverulent oxidic boron compounds, and mixturesthereof, water-soluble materials, alkali metal hydroxides, surfactants,film formers, hydrophobizing agents, preferably organosilicon compounds,silanes, silicones and siloxanes, waxes, paraffins, metal soaps, andcarbohydrates.
 10. The process as claimed in claim 1, wherein theproducing of particulate amorphous silicon dioxide comprising silicondioxide in a proportion of at least 80% by weight, based on the totalmass of the particulate amorphous silicon dioxide, comprises the stepof: mixing two or more different types of particulate amorphous silicondioxide, where the two or more types differ by their particle sizedistribution and/or their chemical composition.
 11. The process asclaimed in claim 10, (i)—wherein a first type of particulate amorphoussilicon dioxide has a particle size distribution having a median in therange from 0.1 to 0.4 μm, determined by laser scattering, and wherein afurther type of particulate amorphous silicon dioxide has a particlesize distribution having a median in the range from 0.7 to 1.5 μm,determined by laser scattering, and/or (ii)—wherein one, two, more thantwo or all of the different types of particulate amorphous silicondioxide is selected or are independently selected from the groupconsisting of particulate synthetic amorphous silicon dioxide containingsilicon dioxide in a proportion of at least 80% by weight, based on thetotal mass of the particulate synthetic amorphous silicon dioxide, andat least carbon as secondary constituent, preferably producible byreducing quartz in an arc furnace; particulate synthetic amorphoussilicon dioxide comprising oxidic zirconium as secondary constituent andpreferably producible by thermal breakdown of ZrSiO₄ particulatesynthetic amorphous silicon dioxide producible by oxidizing metallicsilicon by means of an oxygenous gas; particulate synthetic amorphoussilicon dioxide producible by quenching a silicon dioxide melt.
 12. Theprocess as claimed in claim 10, wherein at least 90% of the grains ofthe granular material having a grain diameter greater than 0.2 mm,preferably greater than 0.5 mm, more preferably greater than 1 mm, ineach case determined by sieving, comprise both or at least two of thedifferent types of particulate amorphous silicon dioxide.
 13. Theprocess as claimed in claim 1, wherein the enlargement step comprisesone or more measures independently selected from the group consistingof: granulating extruding and agglomerating.
 14. A granular materialhaving an average grain diameter greater than 0.2 mm, determined bysieving, for production of a pourable additive for use as a constituentof an inorganic binder in the foundry industry, comprising particulateamorphous silicon dioxide, (a) wherein the granular materialadditionally comprises one, two or more further materials independentlyselected from the group consisting of: particulate materials, preferablyparticulate inorganic materials, preferably selected from the groupconsisting of oxides of aluminum, preferably aluminum oxide in the alphaphase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide,mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphoruscompounds, sheet silicates, graphite, carbon black, glass beads, oxidesof magnesium, borosilicates, ceramic hollow beads, oxidic boroncompounds, preferably pulverulent oxidic boron compounds, and mixturesthereof, water-soluble materials, alkali metal hydroxides, surfactants,film formers, hydrophobizing agents, preferably organosilicon compounds,silanes, silicones and siloxanes, waxes, paraffins, metal soaps, andcarbohydrates, wherein at least 90% of the grains of the granularmaterial having a grain diameter greater than 0.2 mm, preferably greaterthan 0.5 mm, more preferably greater than 1 mm, in each case determinedby sieving, comprise particulate amorphous silicon dioxide, and one, twoor more of said further materials, and/or (b) wherein the particulateamorphous silicon dioxide comprises a proportion of at least 80% byweight of silicon dioxide, based on the total mass of the particulateamorphous silicon dioxide, preferably consisting wholly or partly ofparticulate synthetic amorphous silicon dioxide, and/or (c) wherein theproportion of silicon dioxide in the granular material as a whole,determined by means of x-ray fluorescence analysis, and the proportionof silicon dioxide in at least 90% of the grains of the granularmaterial having a grain diameter greater than 1 mm, in each casedetermined by means of sieving and subsequent x-ray fluorescenceanalysis, differs by not more than 30%, preferably differs by not morethan 20%, more preferably differs by not more than 10%, based on theproportion of silicon dioxide in the granular material as a whole,and/or (d) wherein, in the granular material, the particulate amorphoussilicon dioxide comprises two or more different types of particulateamorphous silicon dioxide, where the two or more types differ by theirchemical composition, wherein preferably one, two, more than two or allof the different types of particulate amorphous silicon dioxide isselected or are independently selected from the group consisting ofparticulate synthetic amorphous silicon dioxide containing silicondioxide in a proportion of at least 80% by weight, based on the totalmass of the particulate synthetic amorphous silicon dioxide, and atleast carbon as secondary constituent, preferably producible by reducingquartz in an arc furnace; particulate synthetic amorphous silicondioxide comprising oxidic zirconium as secondary constituent andpreferably producible by thermal breakdown of ZrSiO₄ particulatesynthetic amorphous silicon dioxide producible by oxidizing metallicsilicon by means of an oxygenous gas; particulate synthetic amorphoussilicon dioxide producible by quenching a silicon dioxide melt and/or(e) wherein the granular material is producible by a process as claimedin claim
 1. 15. A kit for production of an inorganic binder, at leastcomprising, as components in a mutually spatially separate arrangement,a granular material as claimed in claim 14 and a solution or dispersioncomprising waterglass.
 16. An apparatus for performing a process asclaimed in claim 1, comprising a reservoir vessel containing particulateamorphous silicon dioxide, comprising silicon dioxide in a proportion ofat least 80% by weight, based on the total mass of the particulateamorphous silicon dioxide, a mixing or contacting device for mixing orcontacting the particulate amorphous silicon dioxide with one, two ormore further materials, a device for granulating, extruding and/oragglomerating the particulate amorphous silicon dioxide that has beenmixed or contacted with one, two or more further materials.
 17. Theapparatus as claimed in claim 16, additionally comprising one or moreapparatus elements selected from the group consisting of device fortransferring particulate amorphous silicon dioxide from the reservoirvessel into the mixing or contacting apparatus, one or more reservoirvessels containing liquid, preferably liquid wetting agent and/orsuspension medium, preferably water, one or more reservoir vesselscontaining particulate material, preferably particulate inorganicmaterial, preferably selected from the group consisting of oxides ofaluminum, preferably aluminum oxide in the alpha phase, bauxite, oxidesof zirconium, preferably zirconium(IV) oxide, mixed aluminum/siliconoxides, zinc oxide, barium sulfate, phosphorus compounds, sheetsilicates, graphite, carbon black, glass beads, oxides of magnesium,borosilicates, ceramic hollow beads, oxidic boron compounds, preferablypulverulent oxidic boron compounds, and mixtures thereof, one or morereservoir vessels containing a water-soluble material, one or morereservoir vessels containing one or more surfactants, one or morereservoir vessels containing one or more hydrophobizing agents, one ormore reservoir vessels containing one or more carbohydrates.
 18. Theapparatus as claimed in claim 16, additionally comprising a device fordispensing or transporting granular material produced.
 19. Method ofmaking a granular material as claimed in claim 14, comprising the use ofparticulate amorphous silicon dioxide.
 20. Method of producing a solidpourable additive with homogenized grain composition comprising agranular material as claimed in claim 14, wherein the homogenized graincomposition if for use as a constituent of an inorganic binder in thefoundry industry.